Glossary of PNC TermsQ

The following is a list of terms, abbreviations and
acronyms commonly used in Stamp Collecting,
and within the Plate Number Coil Community.

Definitions and explanations are short and may not be all inclusive.

Abbreviations

ABNC		American Bank Note Co.
AP		Ashton Potter
AVR		Avery Dennison
BEP		Bureau of Engraving and Printing
BK		Block Tagged
BN		Back Number
CCL		CCL Label, division of CCL Industries
CSAC		Citizens Stamp Advisory Committee
CPV		Constant Plate Variety
CV - CVP		Computer Vended Postage
EFO		Error, Freak or Oddity
EKU		Earliest Known Use
EP		Embedded Phosphor Paper
FDC		First Day Cover / First Day Cancel
MNH		Mint Never Hinged
NDN		Non-Denominated
OT		Overall Tagged
PV - P/V		Peak Valley
PNC		Plate Number Coil
PNC3		Plate Number Coil Collectors Club
PM		Prephosphored, Mottled Tagging
PMC		Purple Machine Cancel
PMS		Pantone Matching System
PMU		Phosphor Meter Unit
PS		Prephosphored, Solid Tagging
PSA		Pressure Sensitive Adhesive
PSx		Plate Number Strip of x. (x is usually 3 or 5)
SA		Self-Adhesive (Pressure Sensitive Gum)
SFS		Stamp Fulfillment Services
SSP		Sennett Security Products
SV		Stamp Venturers
USPS		United States Postal Service
UT		Untagged
UV		Ultraviolet Light
VP - V/P		Valley Peak
WAG		Water Activated Gum (Lick n Stick)

An automated process that allows mailers to have stamps placed on envelopes by machine. Forms of these machines date back to the 1850s, but they did not become standard equipment until the early 20th century. Stamps affixed by machines often feature clipped or damaged perforations but are desirable on cover to show the use. Here is an image of Postmatic Self-Adhesive affixing equipment.

Quarterly Price List and Newsletter of Stephen Esrati. News and notes about PNCs and Great Americans.

The largest organization of stamp collectors in the United States. Publisher of the monthly journal, "The American Philatelist".

Almost all Self-Adhesive (SA) coil stamps have a backing paper or liner to which the stamps are affixed. There were a couple of experimental Self-Adhesive 'linerless coils' produced that did not employ backing paper. On coils of 100, the liner is the same size as the stamps. On larger rolls, the liner is often larger (taller) than the stamps. Some larger rolls also have space between the stamps on the liner.

Back numbers were introduced on large coil rolls to aid in the process of determining how many stamps remain on the coil. This is useful for internal auditing in the post office, and for those organizations applying postage to mailings using large format rolls. Depending on the starting point of the back numbers, the coil can be either 'odd' or 'even'. An 'even' coil is one where the back number will appear on the reverse side of the stamp with the plate number.

Back Number specialists may collect the various positions of the back number in relation to the plate number as a 'set'. A set may contain three or more back number positions (depending on the wishes of the collector), one of which will be the stamp having both plate number and back number on the same stamp. Here is a handy chart in Excel format.

Stamps having blind perfs appear to be imperforate, but if there is even a trace of a perforation or die-cut dent, it is considered a blind perf.

Stamps having Blind Perforations appear to be Imperforate, but if there is even a trace of a perforation or die-cut dent, it is considered a Blind Perforation.

A multiple arrangement of stamps up to 10 high created from the Sennett Security Products (SSP) attached Stick of vertical coils, which are held together by Bridges. Depending on the placement of the bridge, vertical pairs or blocks of 4 can easily be created. Here is an example of a block. See also Bridge and Coil Block.

Block tagging occurs when tagging is applied to the surface of the stamp in a block shape. The sizes of the blocks can vary greatly with each printing. Some catalogue numbers are assigned by the size of the block alone. The 20¢ Flag over Supreme Court stamps, for instance, received catalog numbers for both wide and narrow block tagging. The rubber mats used for block tagging wear over time and there are unlimited varieties caused by this wearing, including flaking, cracking and breaks. Occasionally the impressions of the stamps are actually worn into the mat, causing them to be tagged with a ghostly transfer image of the design.

A plate strip of 11 with the plate number centered and a back number at each end of the strip.

A Bridge is the tiny tab that holds coil rolls together in a "Stick", about one every five stamps, with the placement randomly staggered in the stamp rows like brick seams in a wall. The term "bridges" was used by Sennett Security Products (SSP) when the 29¢ Tulip was issued in sticks of 10. The bridge on the Sennett 37¢ Flag stick stamps and the 39¢ Lady Liberty stick stamps is the same as that used on the Tulip. Here is a page showing the Flag stick stamps with Bridges.

A paper type used in the production of some press runs of the 34¢ Statue of Liberty WAG stamp. It has a different tagging appearance than the original printing, and can most easily be distinguished by the appearance of the back numbers. British Paper back numbers are composed of dot-matrix numerals, whereas the back numbers on the original printing were solid in appearance. See also Ghost Numbers.

Misalignment of the die cutting knives in the middle of the web. When the knives are correctly aligned, they overlap and create a continuous die cut.

The formed plastic container used for the over-the-counter retail sale of coils of 100 stamps.

The BEP is the branch of the US Treasury Department responsible for printing postage stamps. Once the primary source of modern coils, the BEP discontinued the production of coil stamps effective the end of Fiscal Year 2005.

A pictorial design or inscription on a cover, usually used in conjunction with a first day cancel.

Carets are used to identify the original issue price of ‘Forever’ stamps. In this way, the price is distinguished from the permanent value of 'Service Inscribed' stamps, which are designated by parentheses.

CCL Industries is the company that bought Avery's stamp printing division. It was originally founded in Toronto in 1951 as Connecticut Chemicals Limited. The company currently has three divisions, CCL Design, CCL Label and CCL Container. Its stock symbol on the Toronto Exchange is CCL. When CCL purchased Avery's stamp printing division in 2013, it employed approximately 9,800 people in 87 production facilities in 25 countries on five continents. Corporate offices are in Framingham, Massachusetts and Toronto.

CCL Label is the division of CCL Industries that is now printing U.S. Postage Stamps. They are using the prefix "C" before the plate number.

Centering refers to the placement of the stamp design in relation to the perforations or edges of a stamp. The more perfect the centering (and the larger the margins), the higher the stamp's grade. The more off center the design, the lower the grade of the stamp. Centering plays a very important role in valuing stamps. Many catalogs value stamps in fine to very fine centering - the condition in which most stamps are encountered by collectors. Other catalogs value stamps in very fine condition, a higher quality and less frequently encountered centering, which is worth more. Stamps with nearly perfect centering (superb) frequently sell for multiples of catalog value, while those that are quite off-center (but not misperforated) sell for far less than catalog value. Although centering alone plays a large role in determining the value of a stamp, it does not take into consideration any faults a stamp may have; therefore an undesirable damaged stamp may have superb centering, but may be worth a small fraction of its catalog value.

Denominated stamps issued for use with stocks of previously issued rate stamps to add enough value to pay a new rate.

A double impression left on the printed stamp caused by a set-off from the Chill Roller. Chill rollers occasionally pick up ink from the printed stamps and deposit it on others, creating what collectors refer to as chill roller doubling. See also Printing Terms.

The hardened state of modern printing sleeves. After the metal is hardened, a coating of chrome is applied to help the printing sleeve have a longer printing life. Chromed printing sleeves may be re-chromed.

A die cut variety formed from a misalignment of the cutting die with the printed image on the printing web. Similar to the Bell and Knoll varieties found on stamps printed by Avery Dennison, it is found on 37¢ Flag Waving and 39¢ Crops of America stamps printed by Sennett Security Products, and other issues using the same die cut configuration. Here is the scan of a Cobra Die Cut.

A full roll of stamps as issued by the US Postal Service. Coils normally come in rolls of 100, 500, 3,000 and 10,000. It could also apply to a single 'coil' stamp. The words 'coil' and 'roll' are often interchanged.

Coil labels first appeared in the middle of the late 1950's, a few years after the 1954 Liberty Series debut. Originally, coils were wrapped with paper that not only identified the stamp and its roll size, but also provided a "leader" to thread the stamp dispensing machines. Now coil rolls are wrapped in cellophane and identified with a paper or cardboard label, or packaged in a plastic 'bubble'. These labels come in many shapes and sizes. Here is a study of coil labels.

The original Coil Label Study Group, headed by David LaVergne in 1989, concentrated on PNC labels. Here to view the newsletters. A new, recently formed group, has as its purpose to identify labels from rolls of ALL US coils, including PNCs, in all of their various sizes and colors and to relate them to the actual stamps. Click here to go to the group web page.

The newsletter of the Plate Number Coil Collectors Club (PNC³), published monthly since 1988. Past issues up to three years ago are online at the PNC³ web site, www.pnc3.org. Indexes are also available online.

A stamp issued in a continuous roll, with parallel straight edges on two sides, with perforations or die cuts between the stamps. There have been a few exceptions where coil stamps were issued in a long strip with perforations on all four sides, the most recent being the (5¢) Sea Coast stamp.

A horizontal or vertical multiple of three or more coil stamps in a row. See also Plate Strip.

The seal, label, or wrapper used by stamp printers to package or finish completed coil rolls. Although these items were intended to be removed from coil rolls and discarded, they have become a specialized colleting area, either as an adjunct to coil collecting or as part of a study of stamp printing and processing.

Equipment capable of processing printed webs by slitting into individual rows, perforating or die cutting, rolling and packaging coils of stamps.

A stamp of which the colors have been altered or eliminated by physical or chemical tampering. Certain stamp dyes are susceptible to alteration, especially bleaching by sunlight, heat or chemicals. Color changelings do occur naturally, as in the case of sun bleaching, and they occur as a result of chemicals and other substances that have come into contact with stamps. Color changelings have little philatelic value, except as novelties. Click here to see an example.

Combination perforations can be defined as a stamp having two different hole sizes, and can occur on coils produced by Sennett Security Products as a result of the skiving process that uses three sets of cutting knives spaced across the printing web. Each knife could produce a different size hole, and a given stamp may exhibit two different hole sizes, the change occurring at the point where the knives intersect.

Condition is a prime factor to consider, either buying or selling. Depending on your financial situation, always buy the best you can afford. When it come time to sell your stamps, condition is VERY important. Plan accordingly.

An irregular feature present in the image area of the precancel mat. This variation must occur at regular intervals on the finished product.

Any printed variation of the intended design caused by any irregular feature in the printing process. This variation must occur at regular intervals on the finished product.

A stamp printed in advance of an impending rate increase, for use while stamps bearing the new rate are prepared. These had been 'alphabet' stamps, until the rate increase in 2001, when the contingency stamps were prepared with a design similar to that of the intended design for the next first class coil stamp, and marked 'first class' instead of using the numeric value.

Regular-issue stamps that are kept in use usually for a number of years. Unlike commemorative stamps, definitives can be reprinted as many times as new supplies are needed. Definitives frequently appear as the small postage stamps found on most everyday mail that is intended to supply the most basic postal needs and therefore have been issued in many different, common denominations.

Change in the location of the die cutting mat with respect to the paper web may cause the die cuts on stamps along the strip to change, for example, from PV to bell top or VP to PV.

The number of peaks on opposite sides of a die cut coil stamp. It is usually written as L10/R10 or T10/B10, but can be shortened to 10/10. This indicates 10 peaks on both the left and right sides of a vertically oriented stamp, or on the top and bottom of a horizontally oriented stamp. Several different sizes exist such as 11/12, 12/11 etc.

A stamp separation method used on Pressure Sensitive Adhesive paper. (SA) (PSA) The separation outline can be either straight or serpentine, and is accomplished by crushing the stamp paper fibers without cutting the backing paper on which the stamps are mounted. When looking at a stamp image in its upright normal position, die cutting can be either horizontal or vertical. A couple of coil issues exist with serpentine die cutting on all 4 sides. See also Perforations, Inverted die cuts and Reverse die cuts.

Without Die Cutting. To be a Die Cutting Omitted Error stamp, there must be NO trace of a die cut. Die Cut Omitted coil stamps are usually collected in pairs or larger strips.

When the die cutting on a strip of stamps changes dramatically from one stamp to the next, it sometimes results in different die cuts on both sides of the same stamp. A list of stamps with Dramatic Die Cut shifts is included in the 'Avery Dennison Die Cut Varieties' publication, which is published by the PNC³ Catalog Committee.

Dropout printing is an unprinted portion of the white paper which forms the desired character or other feature in the stamp image.

A low positioned stamp in a strip, resulting from an improperly positioned transfer roller. Also known as a Low Transfer.

Water Activated stamp gum (WAG) having no light reflective quality. It is also referred to as dry gum because there is no shine.

Published every few years by the United States Stamp Society (Formerly Bureau Issues Association), it includes a listing of all known plate numbers and a comparative valuation. Updates and new plate numbers are published in the "United States Specialist", the monthly magazine. A new printing was released in the spring of 2008. The previous issue has a '2005' year date.

The earliest date on which a stamp has been postally used. Many modern stamps have been released early and used on mail before the official first day of issue. In PNC collecting, each different plate number will have an EKU date that may differ dramatically from the first day of issue date for the stamp itself, due to later printing runs for the individual plate.

See Bell. When the misalignment of the die cut mat is severe, the shift in the location of the bell feature occurs completely within the space that should show a normal die cut shape.

See Knoll. When the misalignment of the die cut mat is severe, the shift in the location of the knoll feature occurs completely within the space that should show a normal die cut shape.

Stamp printing paper infused with taggant during the manufacturing process. The paper is uncoated and usually has a Mottled appearance under short wave ultraviolet light. The application of the taggant on this type of paper is much like staining a porous surface; it soaks into the paper and becomes a part of it, appearing throughout the paper fibers. The taggant can not be scraped off without removing some paper. As with Surface Phosphor tagged paper, the printed stamp image appears over the taggant, rather than under.

The last coil stamp printed on Embedded Phosphor Paper, with Mottled Tagging was the 32¢ Flag Over Porch linerless stamp of 1997.

A stamp that is completely missing one or more steps in the printing process, or one that exhibits another serious flaw such as an inverted portion or wrong color, or a double impression. See also Freaks and Oddities.

A process whereby collectors submit their stamps, covers or other philatelic items to recognized experts in the field for their opinions regarding genuineness or condition.

The practice of affixing a lower value stamp or stamps to a bulk mail (standard mail) piece, with the difference from the actual postage cost to be paid at the time of mailing.

Special items created for limited distribution to guests at first-day of issue ceremonies. Such programs not only contain the listing of participants and a program of events for the ceremony, but also examples of the new stamp and a first-day cancel tying it to the program. First-day ceremony programs may be officially produced by the U.S. Postal Service or by a sponsoring organization. The USPS also sells them by subscription.

The Plate Number Coil Collectors Club sponsored a First Day Ceremony in conjunction with the American Philatelic Society for the 41¢ Beautiful Blooms coil and booklet stamps in Portland, Oregon on August 10, 2007.

A cover canceled with the official first day of issue date. The cancellation process is usually done away from the first day site, except for those at the ceremony. A 30 day time extension is usually granted to get covers canceled. More details.

A format in which finished coil stamps of 100 are shipped to the Post Office. Each 'flat' consists of 50 'Bubble Packs'.

A minor plate variety, which generally can only be seen with the aid of magnification.

The Forever designation is applied to stamps issued at the then-current first class value for a one ounce letter, and which remains valid to pay that first class rate at any future date. This is indicated by including the value on this site in Carets < > to indicate the value at the time of issue when referring to the denomination of these stamps. The first Forever Coil Stamps were the se-tenant pair of Statue of Liberty / US Flag Stamps, Scott 4486 to 4491 issued December 1, 2011 with a 44 cent value.

A stamp containing a minor mistake such as a shifted perf or die-cut, miscutting or mis-registered colors.

The unprinted space between the ends of horizontal precancel lines, indicating the seam between the mat or flexographic plate edges. If the gap falls on the 'joint line', it is known as a 'line gap'. Gap also applies to Tagging Gaps. The position of the gap may vary with respect to the plate number on different printing runs. PNC gap collectors frequently seek to acquire all gap positions for a given plate number. See also Seam Line and White Paper Line.

Some rolls of the 34¢ Statue of Liberty WAG issue that were printed on British Paper exhibit ‘Ghost Numbers’. These are faint images of back numbers that occur at intervals between the normal positions of the back numbers on the stamps. This probably resulted from a fault in the wiping process on the press that applied the back numbers.

Gravure printing is characteristically used for long run, high quality printing producing a sharp, fine image. Currently, the dominant gravure printing process, referred to as rotogravure, employs web presses equipped with cylindrical plates (image carrier). Intaglio plate printing presses are used in certain specialty applications such as printing currency and postage stamps. Offset gravure presses are used for printing substrates with irregular surfaces or on films and plastics. Click here for more detailed information. See also Photogravure Printing Process.

A form of plate variety that occurs along the top or bottom row of stamp subjects on a printing plate. Tension cracks occur on printing plates most frequently where the grippers hold the curved plate to the cylinder. These cracks collect ink and deposit it on the printed stamps. Gripper cracks look just like a crack, jagged line, or series of lines running through the stamp design.

Collectors have adopted three categories of gum shine, which is the degree of reflectivity of light on the gum.

Paper that is impregnated with optical brighteners that glow under longwave ultraviolet light. Brighteners are added to the liquid pulp during the manufacture of the paper to enhance the whiteness, and the UV light usually makes these whiteners stand out and shine through any taggant that is applied to the stamp.

See Bell. When the misalignment of the die cut mat is severe, the shift in the location of the bell feature occurs completely within the space that should show a normal die cut shape.

See Knoll.When the misalignment of the die cut mat is severe, the shift in the location of the knoll feature occurs completely within the space that should show a normal die cut shape.

Without Perforations. To be an Imperforate stamp, there must be NO trace of a perforation. Imperforate coil stamps are usually collected in pairs or larger strips. Stamps with 'Die Cutting Omitted' in error are also known as Imperfs.

Pairs or larger multiples of stamps with no perforations or die cuts in one direction, but with perforations on all other sides. A horizontal pair of stamps may be missing vertical perforations or die cuts and be vertically imperf between.

The finished stamps produced by one complete revolution of a rotary printing base. (A base can be a plate, sleeve or cylinder where modern coils are concerned.)

Early self-adhesive coil production by the BEP used a variety of cutting knives in the die cutting mats. These different cutting knives produced incisions in the paper web that are distinctly different in appearance (a good magnifier will clearly show the difference). Three of the die knives produced incisions that leave part of the paper between stamps intact. These intact sections are called 'ties'. Click here for more information and illustrations on Ties and Incisions.

One of many different types of freak varieties that can occur on stamps. Printed by any technique. Inking flaws may range from a small blob of extraneous ink to huge smears or uninked areas. After a line-engraved printing plate has been inked, it is wiped clean, removing all ink that is not in the recessed lines of the plate. Sometimes, either through improper inking or overzealous wiping, too little ink remains in the printing plate to produce a suitable printed image. Such varieties, which are very desirable to collectors, are considered to be defective stamps by the printers and are usually removed and destroyed prior to distribution. As a result, these varieties have additional value to collectors, the value being determined by how significantly the flaw affects the appearance.

The result of a cutting mat being rotated 180 degrees when installed on the mounting cylinder. The shapes, or peak counts, normally found on one side of the stamp become inverted on the opposite side. I.E., The shapes on the right side are the same as normally found on the left side, but inverted. The same situation can apply to horizontal die cuts. A stamp which is normally cut 11/12 exhibits a 12/11 peak count. See also Die Cutting and Reverse die cuts.

Printed line between two coil stamps caused by ink deposited in the seam of two adjoining curved printing plates. The lines can vary from very light to very dark and run the range of the colors on the stamps being printed. Joint lines are a byproduct of intaglio printing from rotary presses that use multiple line engraved plates. Joint lines caused by the Cottrell and Stickney presses used by the USPS ended when the last Cottrell press was retired in 1985. See also Seam Line, Gap and White Paper Lines.

A die cut feature resulting from the mis-alignment of the die cut mat with respect to the stamp image on the printed web. The knoll looks similar to a peak, but is shorter, and occurs when the shape of the die cutting transitions from a PV to VP on adjacent strips from the web. On vertically die cut coils, this feature is always found at the upper left (top) or lower left (bottom). On horizontally die cut coils, the feature is always found either top right or top left. Click here to see scans of a Knoll.

Originally a Printing Press, but now applied to the process of Letterpress, including all forms of relief printing. This encompasses old style block printing, presses with moveable type and flexography.

Almost all Self-Adhesive (SA) coil stamps have a backing paper or liner to which the stamps are affixed. There were a couple of experimental 'linerless coils' produced that did not employ backing paper. On coils of 100, the liner is the same size as the stamps. On larger rolls, the liner is often larger (taller) than the stamps. Some larger rolls also have space between the stamps on the liner.

USPS produced Linerless coils that use stamps as substitute liners. These experimental linerless coils were produced as a conservation measure to help preserve the environment. Examples are the 32c Flag and 25c Jukebox issued on March 14, 1997 and the 33c Berries issued in 2000.

Linn's Weekly Stamp Newspaper, published by Amos Press, focusing on United States stamps, including Plate Number Coils.

A printing process that uses an offset method where the image is transferred to the paper by way of a rubber blanket (mat). Click here for more detailed information.

Water activated stamp adhesive (WAG) that displays a moderate degree of light reflection. Sometimes referred to as Semi-Gloss or Satin Gum. This falls into the range between Dull Gum and Shiny Gum.

U.S. stamps have various styles of luminescents, and Scott minor varieties are often distinguished by the specific luminescent methods used. See Luminescence article by Victor Bove.

Nondenominated stamps issued for use with stocks of previously issued first-class rate stamps in making up the difference between the rate shown and a newly introduced rate.

Microprinting involves extremely small letters or numbers imbedded in the design of selected coil stamps, usually those printed by offset, as a security feature. In most cases, 8-power magnification or greater is needed to read microprinting. Click here to see an example on the Ashton Potter 37¢ Snowy Egret stamp.

A product of Krause-Minkus Publications, Inc. Plate Number Coils are listed in the 'Regular Postal Issues' section, plus there is a special section devoted to Plate Number Coil Strips. Minkus Catalog numbers are used. The Minkus stamp products line was sold to Amos Press in 2004.

Mint generally means 'Unused, in Post Office Fresh condition'. There are a few sub categories, i.e.: Mint-Never Hinged, Mint Hinged and Mint without gum. Plate # Singles, Mint and Used are listed in the Scott Specialized Catalogue under the Used column.

Mint Never Hinged refers to the gum on stamps that have gum without a fingerprint, blemish or mark of any kind. This is the preferred condition in which to save Mint PNCs.

Misalignment between the roll cutting equipment and the web of stamps that causes the stamps to be poorly centered (may result in Plate Numbers at top of stamp or split numbers).

A term that appears on the Data sheets, the Modeler is the person responsible for working the stamp design into a format required for the finished product.

Embedded phosphor paper, in which the stamp printing paper, which is uncoated, is infused with taggant during the manufacturing process produces Mottled Tagging. The appearance when viewed under shortwave ultraviolet light is a rough or blotchy look, as opposed to the smooth or slightly grainy tagging seen on Surface Phosphor coated paper.

The last coil stamp printed with Mottled Tagging was the 32¢ Flag Over Porch linerless stamp of 1997.

A stamp without a denomination. Prepared in advance for use in rate change situations. The actual stamp value when used on this web site is indicated within a set of parenthesis, i.e.: (39¢).

Also applies to Bulk Rate Stamps where the mailer pays the difference between the value of the stamp and the actual postage cost. This practice is called False Franking.

Refers to the stamp in the strip having the back number on the same stamp as the one with the plate number.

Refers to a plate numbered stamp that has been incorrectly trimmed so that the plate number is on the top of the stamp.

Stamps printed for use only by authorized government agencies. As of 2008, only 5 Official Mail coils have had plate numbers.

Stamps with phosphor tagging applied in a lacquer solution to the entire surface after printing. Tagging is applied to the entire printed paper web. The tagging, when viewed under short wave ultraviolet light is even (smooth) or slightly grainy.

A printing industry standardized system of blended colors, each with its own Pantone Matching System (PMS) number. Visit their website at www.pantone.com.

Type I - Paper will usually show some brightness under long wave ultraviolet light and glow bluish white or whitish blue. Gum striations vary from faint to very pronounced, and appear at a 45° to 50° angle. When looking at a type I stamp with backlighting, there appears a 20° criss-cross in the texture, although not all stamps show this pattern.

Type II - The paper and gum usually do not react under long wave ultraviolet light. The gum striations are horizontal and evenly spaced. When looking at a type II stamp with backlighting, there appears a 45° criss-cross in the texture.

Type III - Under long wave ultraviolet light, this paper glows medium bright at the high end all the way to no glow. The gum has no diagonal striations.

The part of a serpentine die cut that protrudes from the side of a stamp. It alternates with a corresponding "valley", or inward curve, to form the serpentine shape. Peak and Valley are abbreviated as P and V. When combined, as in P/V (PV) or V/P (VP), they indicate the shape present at the left top and bottom corners of a vertically die cut stamp. On a horizontally die cut stamp, they indicate the shapes present at the top left to the top right. See scan of a Peak/Valley stamp. Click here for a comparison of the Avery Dennison version.

A row of small holes between stamps to facilitate separation. Modern Plate Number Coils are usually perforated with 9.8 perforations each 2 centimeters. A variety exists in the size of the holes on some stamp issues. LARGE Holes generally are about 1mm and about the same size as the paper between them. SMALL holes are smaller than the paper between them. Click here for a comparison. See also Snowman Perforations.

A device to measure perforations and die-cuts. The gauge is determined by the number of perforations or die-cuts in a 2 centimeter length.

Our web site has a complete list of Philatelic Offices. Because the Postal Service is ever changing, we cannot keep up with changes in the Philatelic Offices and solicit your help to keep current. There seems to be a trend to eliminate Philatelic Offices and replace them with 'Stamp Stores'.

Covers prepared by or sent to a stamp collector. Frequently used as a means of acquiring a used example of a particular stamp, covers of philatelic origin are sometimes considered less desirable than covers that served a purely commercial purpose.

The study and collection of stamps, labels or seals, stamped envelopes and cards, wrapper stamps, their precursory or substitute markings, and their uses, issued for the purposes of postal communications, revenue, charity, promotion, or supplemental to such purposes.

A measure of the relative brightness of the tagging on a stamp. The brightness must be sufficient to activate the automated processing equipment in postal facilities. See Tagging.

Photogravure is generally used for multi-colored stamps and utilizes four basic ink colors: magenta, yellow, cyan and black. A separate plate, which had previously been prepared by photographically separating the colors, is required for each color. Click here for more detailed information. This is the process used to print most current coil stamps.

In the broadest terms, a printing base. A printing base starts as a flat surface, although it may later be curved to fit the press or fit around a cylinder. Plates are made of steel for Intaglio and Photogravure, aluminum for Lithography (Offset), and rubber or plastic for Flexography.

A flaw in the surface of the steel printing plate that accepts ink and adds that ink along with the intended design onto the finished stamp. Generally the flaw becomes progressively larger with continued use, until it is noticed by inspectors and the plate is removed.

The serial number assigned to a plate by the printer. Single digit suffix numbers are printed on the coils as a coded reference to the complete serial number, which is used for accounting purposes.

Beginning in 1981, a small representative plate number appears below the design in the stamps' bottom margin (occasionally within the design).

Last issued in 1995 by Richard Nazar. Originally published annually beginning in 1985 by Stephen Esrati. The numbering system was devised by the Plate Number Coil Study Group.

At the beginning of 2003, PNC³ began publishing its own catalog of Plate Number Coils. The project is designed to be complete in stages. The loose-leaf format catalog will consist of a number of sections determined by design type or usage (e.g.: service inscribed). Early efforts focused on providing information on the latest releases of PNCs along with annual updates of PNC values. In addition to using commonly accepted Scott catalog numbers (under license from Scott Publishing Company), the catalog also assigns unique PNC ID numbers to each discernibly different PNC. This effort is needed because no other catalog publisher distinguishes between many of the collectable varieties of PNCs. Catalog sections and updates are expected to be released at least twice annually.

That's US. You are invited to become a member if you are not already. Please see the Benefits page and then fill out and send in an Application. The dues are very reasonable.

A working group of about 20 people, who did research on all aspects of PNCs and assisted in the production of the Plate Number Coil Catalog. The group has been disbanded, but many of the original members still belong to PNC³.

Many of the early 'Transportation Series' coils were printed on the Cottrell presses, which used two plates in tandem to print the stamps. Thus, two different plate numbers would be paired on a completed printing sleeve, resulting in coils of stamps showing both plate numbers, 48 stamps apart. This arrangement also produced Joint Lines.

A strip of joined coil stamps, including those on backing paper, one of which bears a plate number within its design area. Most collectors prefer to save strips of 5, 7 or 9 with the number on the center stamp. See also Coil Strip.

A coil stamps' position is given in relation to the joint line. Where there is no joint line, an imaginary line, on the perforations or space to the right of the numbered stamp is used. The stamp to the right of the line is 1R and the numbered stamp is 1L. Other positions are counted outward from the 1R and 1L stamps.

Precancels started out with two lines across the face of the stamp, and sometimes contained an inscription between the lines. Eventually the bars were eliminated in favor of a service inscription overprinted or incorporated in the stamp design. The Postal Service still refers to these as precancels, but the generally accepted term is 'Service Inscribed' stamps. Precancels used by bulk mail permit holders do not require any additional cancellation. Precancels or Service Inscribed stamps used by collectors with a 'Precancel User's Permit' do require dated cancels at the time of mailing.

A free permit authorizing a mailer to buy and use precanceled stamps. No fee is required but you must have a permit and you must present your mailing at the office where the permit was issued. View and/or Print a copy of PS Form 3615. Remember that Form 3615 is a multi-purpose form and you need only to fill out Part A, and Check box 2 in Part B.

The final appearance of prephosphored paper depends upon the coating that already exists on the paper.

Paper that has taggant added to the paper during production and prior to printing. There are two types of prephosphored paper: Uncoated Paper and Coated Paper. Uncoated paper tagging will appear mottled under short wave ultraviolet light. Uncoated paper is intended primarily for use with engraved stamps.

Prephosphored uncoated stamps have a mottled appearance under shortwave UV light. The paper is uncoated so the taggant soaks into the paper and pools in the fibers in an uneven way. The result, under UV light is an often fainter tagging, which is occasionally bluish, if the paper also has brighteners added.

Surface coated papers will appear different under UV light depending on how the paper is manufactured and how the taggant material is applied. The coating may be smooth, uneven, or slightly grainy. Since prephosphored stamps have the design printed over the tagging, the stamp design usually appears much bolder in comparison to overall tagging. (With Overall Tagging the design is under the tagging).

A Press - A Five-color Gravure and Three-color Intaglio Giori webfed combination press used by the BEP starting in the early 1970s. Officially known as Press 702.
B Press - Three-color Intaglio Giori webfed press used by the BEP starting about 1976. Officially known as Press 701.
C Press - Three-color Intaglio Giori webfed press used by the BEP starting about 1982. Officially known as Press 901.
D Press - Six-color Offset and three-color Intaglio Goebel webfed combination press. In use about 1984. Officially known as Press 902

Andreotti Gravure Press - An Italian made press, purchased by the BEP in 1970 primarily for commemorative stamps, but coil production started in the 1980s. Officially known as Press 601. Water Activated stamps are printed from plates of 432 (18 x 24) and 480 (20 x 24). Pressure Sensitive Stamps are printed from plates of 378 (18 x 21) and 480 (20 x 24).
This same model press has been used by Guilford Gravure, a subcontractor for American Bank Note Co. The plate size is 456 stamps per revolution (19 x 24).
Champlain Press - J. W. Fergusson & Sons, a subcontractor for Stamp Venturers, prints utilizing a layout of 13 rows of 33 stamps.
Cottrell Presses - Single-color webfed Intaglio presses used at the BEP for almost 30 years, starting in 1956. Officially known as Presses 801, 802, 803, 804 and 805.
Dia Nippon Kiko Press (DNK) - Process Gravure Printing Press used by Avery Dennison, and CCL Label, after the latter purchased the Avery Printing Division. Pressure Sensitive Stamps have been printed from plates of 300 (10 x 30), 320 (16 x 20), 385 (11 x 35), 396 (11 x 36 and 12 x 33) and 480 (12 x 40). There may be other impression sizes depending on the stamp being printed.
Muller Martini, A76 - A 27" Process Offset Press used by Ashton Potter. The plate size is 744 (24 x 31) coil stamp impressions per revolution.
Optiforma Presses - Six-color webfed Goebel Offset presses put in coil service about 1985. Officially known as presses 42 and 43.
Schiavi Press - Multi-Color Corp., a subcontractor for American Bank Note Co., uses this press that prints 684 stamps per revolution (19 rows of 36).
Updated information on printers and presses used can be seen on the data pages for new issues.

Purple ink was used in tests in the 1970s for canceling purposes because the existing black ink often jammed machines and slowed down operations. Purple ink was used in 131 cities primarily from 1980 thru 1983. It was criticized because it was hard to read and would run and discolor stamps and the cancel could be washed off stamps. It was phased out when a new black ink was developed in 1982. Here is a list of Plate Number Coils with Purple Machine Cancels.

Die cutting from a new design of a die mat, but still exhibits the same peak counts as the original. For example, a mat that
produces a 10/10 peak count has a peak/valley (PV) sequence starting with a peak in the upper left corner of the stamp. The new design starts instead with a valley and results in a VP sequence. Both still have a 10/10 peak count. See also Die Cutting and Inverted die cuts.

On a self-adhesive stamp, the section of the die cut that normally would be between two rows on properly sliced coils. This section can be: straight, either horizontal or vertical; slanted, either sloped left or right; or a half height dome shaped cut called a knoll. The straight section could be vertical (on a horizontally formatted coil), horizontal (on a vertically formatted coil), or at an angle, sloping to the left or the right.

Water activated stamp adhesive (WAG) that displays a moderate degree of light reflection. Sometimes referred to as Low Gloss or Semi-gloss Gum. This falls into the range between Dull Gum and Shiny Gum.

Each year, Scott Publishing Co., issues two catalogs containing information on Plate Number Coils. The Scott Standard, Volume 1, comes in the Spring. The Scott Specialized appears late in the year and is more comprehensive in its coverage of PNCs. Both use the Scott numbering system, which is accepted worldwide.

A colored line or lines between two coil stamps caused by ink build-up deposited on the printing blanket from the edge of the offset plates. The lines can vary from very light to very dark and run the range of the colors on the stamps being printed. See also Joint Line, Gap and White Paper Line.

The reverse side of a stamp that is coated with a pressure sensitive coating that sticks without the use of moisture. Most US Self-Adhesive coil stamps are sold on a removable liner.

The unprinted paper surrounding the coil stamp. The term also refers to the paper that borders sheets and panes of stamps as they are printed.

Water activated stamp adhesive (WAG) that displays a moderate degree of light reflection. Sometimes referred to as Low Gloss or Satin Gum. This falls into the range between Dull Gum and Shiny Gum.

Precancels started out with two lines across the face of the stamp. Eventually the bars were eliminated in favor of service inscription overprinted or incorporated in the stamp design. The Postal Service still refers to these as precancels, but the generally accepted term is 'Service Inscribed' stamps. Precancels used by bulk mail permit holders do not require any additional cancellation. Precancels or Service Inscribed stamps used by collectors with a 'Precancel User's Permit' do require dated cancels at the time of mailing.

Sennett is a security printer contracted by the USPS to print postage stamps. Sennett, in late 2015, purchased the stamp printing operations of CCL Label, and its subsidiary, Banknote Corporation of America, to produce postage stamps under USPS contract. Plate numbers on stamps are prefixed by “S”.

A die cut feature resulting from the misalignment of the die cut mat with respect to the stamp image on the printed web. The shallow valley looks similar to a valley, but is shorter, and occurs when the shape of the die cutting transitions from a VP to PV on adjacent strips from the web. On coils with vertical serpentine die cuts, this feature is always found at the upper left (top) or lower left (bottom) of the stamp. On coils with horizontal serpentine die cuts, the feature is always found either top right or top left. (See Fig. 8.) Shallow valley die cuts occur only on stamps produced by Avery Dennison. More information can be found in the catalog chapter Avery Die Cut Varieties.

Water activated stamp adhesive (WAG) that displays a moderate degree of light reflection. Sometimes referred to as Low Gloss or Satin Gum. This falls into the range between Dull Gum and Shiny Gum.

Water activated stamp adhesive (WAG) having a high light reflective appearance. Sometimes referred to as wet gum.

On a self-adhesive stamp, the section of the die cut that transitions from the serpentine die shape to the straight die shape. Shoulders are known to be either rounded or squared (at a 90° angle). Click here to see examples.

Material, usually glue or a similar substance, incorporated into all finished papers during manufacture to keep the ink from bleeding through the paper fibers and to add stiffness.

A perforating process used by Sennett Security Products (SSP) which employs truncated cones (with slightly rounded tops) on the form cylinders that push on the stamp paper from the front while steel rotary cutting blades scrape off the paper from the rear.

There are three staggered sets of cylinders and cutters, the last two downstream of and overlapping the preceding set. The three sets together span the entire width of the paper web.

Misalignment of the overlap causes crooked (offset) hole rows, “snowmen”, and the overlap can cause hole size variation within a single stamp if one of the cylinders is worn more than the other. Wear of the cones due to contact with the paper causes smaller perf holes, not larger holes. Wear reduces the height of the cones, causing less paper to be removed and thus a smaller hole. See Snowman Perforations.

A seamless steel cylinder used in line engraved intaglio printing. The images to be printed are entered directly on the curved surface.

The mechanism for separating the printed web into individual rows to form continuous strips that are cut to length and rolled into coils.

Smooth tagging occurs when taggant is applied to the surface of a coated paper by the paper manufacturer prior to delivery to the printer. It has a smooth, usually solid appearance when viewed under shortwave ultraviolet light.

A perforation anomaly that appears on some stamps processed on what is known as an APS grinding perforator. The name comes from the appearance of the anomaly: stacked perforation holes that resemble a sideways snowman. The APS grinding perforator does not punch holes in the stamp paper; it grinds out the holes, with the use of three rotary blades and a perforation pattern die that pushes the paper into cutting blades, producing dust, rather than tiny circles of paper. The practice is known as skiving. Cutting heads are positioned so that the printed web first travels past one cutter, grinding away the paper and perforating that portion of the web first. The web then travels under a take-up roller to the remaining two cutting heads. If the paper slips slightly out of alignment, or if the take-up rolls develop play or chatter, the edges of the blades, which normally overlap two or three holes, double-cut the stamps out of alignment, causing the snowman affect of slightly doubled perforations. See Skiving.

The Plate Number coil Collectors Club is discouraging the use of the term 'Solid Tagging', preferring instead to use Smooth Tagging. Smooth tagging occurs when taggant is applied to the surface of a coated paper by the paper manufacturer prior to delivery to the printer. It has a smooth, usually solid appearance when viewed under shortwave ultraviolet light.

A damaged or inferior copy of a stamp valued chiefly for its ability to fill a spot in an album. It is assumed that the stamp will be replaced when a better example is obtained, unless it happens to be very rare or valuable.

A taped joint connecting two pieces of a roll of stamp paper while still on the press. Used to repair broken webs or extend the length of a given roll. Splices, which are normally red or clear adhesive tape, can be found with printing on them.

A Weekly, then Bi-Weekly Stamp Newspaper formerly published by Krause Publications, Inc. The Minkus stamp products line was sold to Amos Press in 2004 and the final issue of Stamp Collector is dated 5 July 2004.

A regional USPS site that distributes postal items to Stations, Branches and Associate Offices. Usually referred to as the 'Accountable Papers' office.

The mail order arm of the United States Postal Service, located in the 'caves' beneath Kansas City, MO. They publish a free quarterly catalog.

As many USPS Postal Retail Outlets are remodeled, the move is toward the Stamp Store, a place where stock is displayed on the wall and available for inspection before purchase. There are some items that are impractical to display, such as large coil rolls, and most Stamp Stores do not display coils at all.

Stick refers to a vertical stack of two or more coils (up to ten) held together by "Bridges". Most stamps in coils of 100 produced by Sennett Security Products (SSP) are in this configuration, including the 29¢ Tulip, the 37¢ U. S. Flag, the 39¢ Lady Liberty, the 39¢ Official the 39¢ Crops of the Americas. Click here for an illustration. See also Block.

Any perforated stamp with one or more sides without perforations. Straight edges occur both naturally and as damage to a stamp. As damage, a straight edge is easily and often accidentally created by a pair of scissors or a letter opener. Most modern-day water activated and self-adhesive coils have naturally occurring straight edges, produced when the coils are sliced into rolls. Most self-adhesive coil stamps from rolls of 3,000 and 10,000 are die cut with straight edges on the top and bottom.

Stamp printing paper, usually coated papers for stamps printed by gravure or offset lithography, treated with taggant that adheres to the surface of the paper. Applied by the paper manufacturer prior to delivery to the printer, its appearance may be either a smooth, usually solid appearance, or uneven when viewed under short-wave ultraviolet light. Surface phosphor paper usually appears solid, but the appearance could change depending on how the tagging was applied (sprayed on or rolled on). The smooth or uneven appearance is not an indicator of type. The tagging can be carefully scraped off without damaging the paper.

A phosphor solution, either on the stamp or in the paper, that is usually invisible in normal light. A few issues have had the taggant blended into the printing ink.

The process of adding a taggant material to the paper or as a separate application in the printing to produce a phosphorescent or luminescent reaction under ultraviolet light. Block tagging can sometimes be seen by holding the stamp at an angle to a bright light source. Tagging is used to activate postal processing machinery. Self-Adhesive stamps which are tagged appear either smooth or uneven.

USPS Paper Type I is Embedded Phosphor Paper. Type I paper has a PMU (Phosphor Meter Unit) of 175 +/- 25.

USPS Paper Type II is Surface Phosphor Paper. Type II paper has a PMU (Phosphor Meter Unit) of 225 +/- 25.

USPS Paper Type III is untagged paper. Type III paper has a PMU (Phosphor Meter Unit) of 0. Most modern stamps with a value under 10¢ are intentionally untagged.

Many collectors tend to classify tagging types by appearance alone. It is important to accurately classify paper type (embedded or surface) first, visual appearance (mottled, smooth or uneven) secondarily. See the September, 2008 issue of Coil Line.

A strip of stamps with regularly recurring interruptions in their overall tagging. Usually the break, an untagged area, consists of a vertical bar, but other shapes are known.

Coil Test Stamps were created primarily to test tension chocks in coil vending equipment and stamp affixing machines. In addition, they can be used for training purposes and mailing demonstrations.

The Bureau of Engraving and Printing (BEP) produced most of the Test Coils, but in more recent years, private contractors have also produced a few Test Coils.

When the last row of a VP die cut stack is cut too low, a thimble bottom die cut is formed from the vertical die cut straight line. A thimble top is formed when the VP on the top row is cut high. Click here to see scans of the Thimble Variety.

A Tie is the connecting portion in an Incision between Pressure Sensitive Adhesive (PSA) stamps. References include TTL (tie tip left) and TTR (tie tip right). Refer to Coil Line issues: (Snippets 8/98 and 9/98) and (Nazar 9/98). Click HERE for more information on Ties and Incisions.

A steel cylinder bearing a raised image taken from an engraved master die, used to transfer a single original intaglio design to the multiple-subject printing plate.

The person who selects and arranges the style and size of typeface for the lettering and numbers in a stamp design.

Longwave UV light detects tagging on many types of foreign stamps, watermarks and optical brighteners, such as those in 'Hi-Bright' paper.

Short-wave UV light detects tagging on almost all US stamps.
CAUTION: Short-wave UV light can be very harmful to the eye (may even cause blindness!).

Surface Phosphor coated paper usually appears solid, but the appearance could change depending on how the tagging was applied (sprayed on or rolled on). The appearance may be either a smooth appearance, or uneven when viewed under short-wave ultraviolet light. The smooth or uneven appearance is not an indicator of type. The tagging can be carefully scraped off without damaging the paper. Surface Phosphor Tagging began with the 25c Flag Over Yosemite, Scott #2280.

In contrast, Mottled Tagging is on Embedded Phosphor uncoated paper, the appearance of which when viewed under shortwave ultraviolet light is a rough or blotchy look The last coil stamp printed with Mottled Tagging was the 32¢ Flag Over Porch linerless stamp of 1997.

An organization of stamp collectors interested in United States Stamps. Plate Number Coils are often included in the monthly journal, The "United States Specialist". The organization was formerly know as "The Bureau Issues Association" (BIA).

A stamp printed without tagging, either purposely or in error. Most modern stamps with a value of 10¢ and under are intentionally untagged.

A part of the serpentine die cut that intrudes into the side of a stamp. It alternates with a corresponding "peak", or outward curve, to form the serpentine shape. Peak and Valley are abbreviated as P and V. When combined, as in P/V (PV) or V/P (VP), they indicate the shape present at the left top and bottom corners of a die cut stamp. On a horizontally die cut stamp, they indicate the shapes present at the top left to the top right. See scan of a Valley/Peak stamp. Click here for a comparison of the Avery Dennison version.

A machine vended coil stamp whose denomination is printed on the stamp at the time of sale by the machine. Sometimes referred to as "Variable Rate Coil" or "Computer Vended Postage".

A large roll of rotary press printing paper on which stamps are printed in a continuous operation.

"White paper line" is the absence of color where there should be some and shows as a vertical unprinted area between stamps. See also Seam Line and Gap.