In the study of mint errors and varieties, identification numbers are even more abundant than with the regular segment of the hobby. These numbers are simply easy methods of identifying various varieties. By using these numbers, other specialist can quickly and easily determine exactly which variety is being mentioned. Other numbers are used to describe rarity, and even a certain class or type of variety.

Most of these identification systems are simply numbers listed after the date and denomination. Some, more complex identification listings include letters or symbols to further identify the variety or error. Additionally, some of the identification listing can be confusing, as a couple use the same prefix. In this case, one must be able to assume which identifier the writer is mentioning.

Rarity factors

The Sheldon Scale

For many years, the only method of commonly identifying rarity was the Sheldon Scale. This scale was designed to identify rarity of Large Cent varieties. In this case, this scale worked very well, as mintage figures were relatively small. The Sheldon Scale was adopted for use with many other series and denominations, as it was the only common scale in existence. However, it was not quite appropriate for some indications.

The Sheldon Scale was simply a progression of eight places, in which the population of all Large Cent varieties were to fall, and was prefaced with the letter "R", indicating rarity.

The Sheldon Scale

R-1 Common R-2 Not So Common R-3 Scarce R-4 Very Scarce (population est at 76-200)

R-5 Rare (31-75) R-6 Very Rare (13-30) R-7 Extremely rare (4-12) R-8 Unique or Nearly So (1,2 or 3)

As we indicated previously, other writers adopted this scale to represent coins that were considered scarce or rare, however, as you can imaging, the scale would not be appropriate for many coins. For instance, under this scale, the 1955 doubled die Lincoln Cent would be considered common or not so common.

The Universal Rarity Scale

It is quite obvious from the above that another scale was desperately needed by the hobby for indicating rarity of all coins. Leave it to Q. David Bowers to recognize the need, and develop a method that could be used for any series, and any rarity. Bowers developed The Universal Rarity Scale (URS), which as its name implies, is universal for any coin or item. Bowers outlined his scale in the June 1992 issue of The Numismatist. It has already been adopted by many writers and catalogers.

The Universal Rarity Scale by Q. David Bowers

URS-0 None known URS-1 1 known, unique URS-2 2 known URS-3 3 or 4 known URS-4 5 to 8 known URS-5 9 to 16 known URS-6 17 to 32 known URS-7 33 to 64 known URS-8 65 to 125 known URS-9 126 to 250 known URS-10 251 to 500 known

URS-11 501 to 1,000 known URS-12 1,001 to 2,000 known URS-13 2,001 to 4,000 known URS-14 4,001 to 8,000 known URS-15 8,001 to 16,000 known URS-16 16,001 to 32,000 known URS-17 32,001 to 65,000 known URS-18 65,001 to 125,000 known URS-19 125,001 to 250,000 known URS-20 250,001 to 500,000 known etc.

As you can see by the Universal Rarity Scale (URS), the mathematical progression is simple, and can be applied to any item as an indication of rarity. In addition, the scale, being simple, does not require memorizing the scale, as one can figure what population a URS number indicates.

When using rarity numbers, there are a couple of things to remember. One, rarity generally differs from one grade to another. If a coin is listed as URS 13 (2001 to 4000 known), it may be relatively common. However, if there are only 2 known in grades above AU, it would be a true rarity in MS63. Such is the case with the 1888-O Morgan Dollar, "hot lips" variety. They are fairly common is VG and F, but unknown above AU.

Secondly, rarity and value are not as closely related as one might suspect. If there are 10 examples of a particular variety known, but only 7 or 8 collectors interested in obtaining a copy, the coin would certainly be rare, but because of a relatively low interest factor, it would not command much of a premium. Conversely, there could be many thousands of a variety known, but if many thousands more collectors were interested in obtaining a copy, the premium over the normal value of the coin would be greater due to the high interest factor (demand). This brings us back to the old theory of supply and demand.

Interest factor

Interest factor is a term used to indicate just how much demand a particular coin or variety might have. A variety with a very high interest factor would be in high demand, with thousands of collectors desiring the variety. A medium interest factor may indicate that the variety is desired by hundreds of people, and a low interest factor might indicate that the coin is sought by just a handful of collectors.

The interest factor, combined with the rarity, help to determine the value of a certain variety or error. However, the eye appeal of the variety or error is also a contributing factor and must be considered in the final evaluation. A very important part of eye appeal is the relative strength or visibility of the particular variety or error - how easily can it be seen?

As a variety receives more publicity within the numismatic press, the Interest Factor may rise as demand increases. This may cause the price or value of certain varieties (and errors) to increase without any change in the estimated quantity available. On the other hand, if a large quantity of a variety surfaces, the value of that variety may decrease as the supply outstrips the demand.

As in other segments of the hobby, a combination of supply and demand almost always dictates the price or value of a particular variety.

RPM and OMM listing numbers

You will notice that most RPMs (repunched mintmarks) and OMMs (over mintmarks) are identified simply, such as 1938-D/S 5c, OMM #1. These numbers simply indicate that the coin is a 1938-D nickel, with an over mintmark (D over S), and is over mintmark #1. This indicates that it was the first OMM listed for that particular date by John Wexler and Tom Miller in The RPM Book. The RPM Book has become the standard in the hobby for RPM and OMM reference.

The same holds true for repunched mintmarks. If a coin is listed as a 1960-D 1c RPM #1, it simply means that the coin is a 1960-D cent, and is the first RPM listed for the date. RPM #1 does not necessarily indicate that the RPM is the strongest or the rarest, only that it was the first one to be listed.

Doubled die listing numbers

As with the RPMs and OMMs, the doubled dies are also assigned numbers which correspond to the listing numbers in the CONECA files. These numbers can be confusing to the beginner, so a brief explanation is included herewith.

There are seven basic classes of doubled dies. These classes have nothing to do with the strength of the doubling, but rather indicate how the particular doubling occurred. Because of the complexity, the "how" is covered in other handouts. For example, there is a Lincoln Cent listed as 1971-S PF 1c 1-O-II. These numbers indicate that the coin is a 1971-S Proof 1c, listed as die #1, with the doubling on the obverse, and it is a class II doubled die. As with the RPMs, if the coin is die #1, it does not necessarily mean that it is the strongest doubled die for that date, only the first one listed.

The sequence for these doubled die listing numbers will always be the same. Following the date of the coin will be the indication of a proof (if it is a proof), then the denomination, the die number (indicated by Arabic numerals), an "O" or "R" signifying obverse or reverse, then finally the class of doubled die (indicated by Roman numerals). There are some doubled dies which have more than one class, such as 1971-S PF 1c 2-O-II+V-CW. The "CW" at the end indicates the spread is in a clockwise direction. Class I and Class V doubled dies will be indicated with a CW or a CCW, indicating either clockwise or counter-clockwise spread. There are also cases in which a coin will have a doubled die on the obverse and reverse, such as 1963 25c 7-O-II + 1-R-I.

A more detailed description of each doubled die class is published in The Lincoln Cent Doubled Die by John Wexler. This book is highly recommended for all variety enthusiasts.

Other numbers

Other numbers are used from time to time to usually indicate a listing number is some reference book. A list of these is shown below. This list may not necessarily be complete, as more books and reference works are being produced constantly.

Breen - Listed in Walter Breen's Complete Encyclopedia of U. S. and Colonial Coins.

FS - Fivaz/Stanton, listed in The Cherrypickers' Guide.

S - Snow, listed in Flying Eagle and Indian cents, by Rick Snow.

VAM - Van Allen/Mallis, Morgan and Peace Dollars as listed in Comprehensive Catalog and Encyclopedia of Morgan and Peace Dollars.

Leone - listed if Frank Leone's Longacre's Two Cent Piece Die Varieties and Errors.

Sheldon - Listed in Penny Whimsy by William H. Sheldon

WB - Listed in The Complete Guide to Liberty Seated half Dollars by Randy Wiley and Bill Bugert