P is for Plate Number Coil

What's a Plate Number Coil?

See the tiny number "8" at the bottom of the center stamp?
(click on image for enlarged version)

If you don't use coil stamps, even the word "coil" may be new to you, but businesses, the Post Office itself, and many individuals use them extensively. A coil is a long strip of stamps with no perforations at top or bottom - just on the sides, like the strip shown above - rolled into a coil so it can be inserted into some sort of dispenser and fed out one at a time. If you have ever bought stamps from the vending machine in a Post Office lobby, you probably bought coil stamps. They are also available in rolls of 100 from Post Office windows, and by mail in rolls of 500, 1000, even 5000 and 10000 from the Postal Fulfillment Center in Kansas City.

A Plate Number Coil (abbreviated PNC) is a coil stamp with a plate number on it, usually at the bottom of the stamp, below the design. Every printing plate for stamps has such a number assigned to it. The plate number uniquely identifies each plate for a particular design (there was a time when plate numbers were unique among all stamps printed up to that time, but that practice is now long dead). Since each plate can print many millions of stamps, many stamps will have only one plate, and therefore only one plate number. Others are printed in huge quantities - billions - and need many plates, each with its own number. Only one coil stamp in every 20 or more will have the number, so in an entire roll of 100 stamps, only a few will have the number. That scarcity, plus the connection the numbers provide with the production of the stamps, makes them a popular collecting specialty for U.S. collectors. The accepted way of collecting them today is in strips of five, with the plate number on the center stamp.

What follows on this page is the text of an article I wrote six years ago. I may revise and update it some day, but decided it was OK to start with it as-is, since the information contained is still fairly accurate. Prices must have changed, and there must be a few more varieties and plates known by now, but what I say below should be substantially correct.

(The article below was published originally in the September, 1996 issue of The American Philatelist,
with whose permission I am reproducing it here.)

Collecting Plate Number Coils

As with many aspects of stamp collecting, only you can determine the "right" way to collect plate number coils ? right for you. One common approach is to seek an example of every known plate number in a mint strip of three or five. A regular column in Linn's features a table of verified plate numbers on PNCs. Reputable dealers specialize in the area and can sell you a complete collection. The last time I checked, there were about 530 known numbers, with a retail value of about $6,000. Leave out the forty most expensive (total cost of just these forty is more than $3,900), and the price is a bit more reasonable ? about $2,100.

Personally, I prefer to collect major production varieties ? differences in tagging, paper, and gum. I am generally not interested in rarities and errors, freaks, and oddities, partly because they tend to be expensive, but mainly because they represent accidents. I am more interested in the intentional varieties, and how and why they came about. The fact that ten different plate numbers on an issue exist does not interest me. What does interest me is the fact that half of them have a shiny gum and the other half a dull gum, or that some are tagged, while the rest are not. Investigating these distinctions has taught me about the different printing presses used in stamp production, about letter sorting and canceling methods used by the USPS, and about changes in technology in both stamp printing and mail processing over the last fourteen years. Some collectors go even further and look for different types of paper and minute differences in gum, but those distinctions are too subtle for me.

I collect plate number coil production varieties in three ways: as singles, as pairs, and as plate number strips of five, with the goal of including one example of each format for every major variety. For many issues, there is only one variety. Others have as many as four. Any plate number will do for me, so long as it represents a particular variety. The key factors in defining a distinct variety to me are (1) that it was intentional; (2) that I can identify it on any single mint stamp, independent of the plate number; and (3) that it is relatively plentiful. For example, the plate number A3 variety of the 5-cent Circus Wagon coil, whose ink glows under ultraviolet light, qualifies nicely, while the so-called "Lenz paper" variety of the 29-cent Flag and Mount Rushmore, although it conforms to my first two standards, fails on the third. This might seem arbitrary, but it is my collection, so I get to make the rules. (I also get to break the rules, so I choose to include a few accidents and errors that are in relatively plentiful supply, such as the tagged error of the BEP Eagle and Shield bulk rate stamp.)

To date (January 15, 1996), I have confirmed 167 PNC varieties that meet my criteria. On page 2 of this article I have listed all these PNCs, with key identifying features for each variety. I offer my list in hopes that it may assist other collectors just getting started in this collecting area. After all, one of the satisfactions of collecting is achieving completion. Without a list like this, how will you know when you have everything?

Some of the notations may appear a bit cryptic but should be intelligible if you study my Terms and Abbreviations, the stamps themselves, and the published literature (see my list of references). The only special equipment you will need is a shortwave ultraviolet lamp to see the tagging and a precise millimeter gauge for measuring the designs. Be sure you use a shortwave lamp made for detecting tagging on U.S.stamps. I use the Raytech Versalume lamp. The Scott Uvitech Micro SC lamp works well, too. The Lighthouse shortwave lamp works only if you get the optional filter. All of these are battery-powered, but also very portable. If you are willing to spend at least a hundred dollars, there are non-battery UV lamps that are sturdier and more reliable, but not portable. For precise design measuring, I use the Phil-A-Meter gauge, available from many dealers. And in some cases it may be helpful if you make templates out of stiff paper to measure key design elements.

The retail prices I quote are typical ones from recent (on 1/1/96) dealer ads, for the cheapest example of each variety. You may be able to do better, especially on the more expensive items. The cost of assembling a complete collection "my way", in plate number strips of five, should be under $1,000. If you skip the twelve that cost more than $15 each, the cost should be around $500. A collection of singles should not set you back more than $100. Most of the varieties are stocked by dealers as such, so you should have no trouble locating them. A few ? especially some of the tagging varieties ? will be tougher, especially as singles or pairs, but if you are like me, you will enjoy the hunt for those most of all.

If you do not like the rules I have used to define what belongs and what does not, make your own rules. Exclude some of the distinctions that I have made and make the task easier. Look for additional differences and make it more difficult. It is your collection. Have fun with it. I have certainly enjoyed mine. If you are a joiner, or simply want the company of other PNC collectors to simplify your search for elusive material, join the Plate Number Coil Collectors Club (PNC³). For information, visit their excellent web site.

Are the Transportation Series coils dead? The U.S.Postal Service claims it will issue no more new designs in this popular series, which has sustained this collecting area for more than ten years. No need exists for an additional design in this series, unless a rate change occurs ? an unlikely event for another two to three years {it finally happened in January, 1999 - from 32¢ to 33¢; and again to 34¢ in January of 2001}. Given its age and size, the series indeed may be coming to an end. Depending upon your perspective, that means this is either a good time to start collecting the area ? you can complete a collection quickly ? or the time to collect some other group of PNCs, where there is still the thrill of the hunt for new numbers and varieties. It is your choice. Clearly the USPS intends to continue issuing coils with plate numbers. Who knows? Soon they may start putting a plate number on every stamp.

The new back numbers are being pursued by some collectors, but there is no agreement yet about the proper format. Should you collect a plate number strip with the back number on the same stamp as the plate number? Or a strip of seven, with the back number four to the left of the plate number stamp, so that you can fold over the back number stamp and display both plate number and back number at the same time? Or something else? The ink used for back numbering leaks through to the front in some cases, apparently, perhaps ruining the stamp. Perhaps collectors should avoid back numbers. On the other hand, back numbers can allow us to distinguish in which size roll a stamp was sold, creating a whole new area of specialization. I am accumulating examples and trying to decide whether I care about this new twist.

Finally, what about the new self-adhesive coils? Unlike the self-adhesive booklets, which have caught on in a big way with the public (for their convenience) and with collectors (for their appeal as a new challenge), the coils have yet to gain popularity. One reason may be that until recently they were available only from the Philatelic Fulfillment Service Center. Another is that they are not yet easy to use. It is probably only a matter of time before someone develops an automatic affixing machine that will handle self-adhesives; then these, too, can find a legitimate place in the market. To me, self-adhesive coils belong in a new category anyway, so I have not included them here.

Link to page 2 of this article, my table of all the varieties through January, 1996

References and Recommended Resources

The 1995 Plate Number Coil Catalog (eighth edition), Compiled by the PNC Study Group of the PNC Collectors Club (PNC³), and edited by Richard J. Nazar. At its time this was the ultimate reference work on the topic. There may be a newer edition by now. An essential reference for collectors of this material.

Linn's Stamps That Glow, by Wayne Youngblood, offers a useful introduction to and overview of tagging. This handy booklet is out of print but may be available from dealers of philatelic literature. Another source for this and other philatelic literature is the "Philatelic Literature Clearinghouse" in the PLR, the quarterly publication of the American Philatelic Research Library, P.O. Box 8000, State College, Pennsylvania 16803.

Handbook on U.S. Luminescent Stamps, by Alfred G. Boerger, one of the pioneers of the study of tagging on U.S. issues, is an informative collection of statistics, definitions, and advertisements. Mr. Boerger died recently (October, 2001), so you will probably have to get this from a literature dealer.

Linn's Plate Number Coil Handbook, by Ken Lawrence also is out of print but makes an excellent reference for students of PNCs. Although the book covers only those PNCs issued through mid-1989, it remains an impressively complete and accurate source of background information on these stamps, as well as a source of detailed statistics about them.

Linn's U.S. Stamp Yearbook, published yearly by Linn's Stamp News - These are great books, issued yearly by Linn's since 1983, and providing newsy, entertaining data and stories about the production of every U.S. stamp issued for the year covered. They are the worthy modern equivalent of the works of Brookman and Johl, and provide both fun reading and useful reference.

The Author, William Senkus, a computer systems analyst, collects trains on stamps - indeed trains on almost anything, plus 26 collections of various sizes related to Alphabetilately, his philatelic alphabet.

The above article was originally published in the September, 1996 issue of The American Philatelist, with whose permission I am reproducing it here. The original title was "Collecting Plate Number Coils".

If you are interested in stamp collecting, and not yet a member of The American Philatelic Society, I recommend you join - my own membership has increased the value and enjoyment of my stamp collecting activities immeasurably. Click on their logo above to visit the main page of their web site and learn more.

Second Page of PNCs article

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All text Copyright © 2001, William M. Senkus

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Revised -- 11/28/2001