Coin Monday: Mysterious Missing Mintmarks

June 15, 2009
Posted by John Dale

The mintmark is a simple concept nearly as old as coinage itself: it is a small letter or symbol that signifies where a coin was struck. The official U.S. Mint Web site has an excellent summary of the mintmark as that agency uses it today; now, as in the past, a mintmark can be used to trace a defective coin back to its source. Since the mintmark is itself part of the coin, though, it is not immune to its own class of errors, many from the days when mintmarks were punched into dies by hand. The most dramatic of those errors happens when the mintmark is left off entirely, as it was on this “No S” 1990 proof cent.

Depending on the circumstances, a missing-mintmark error can be obvious or practically invisible. For most of its history, the Philadelphia Mint did not use a mintmark to distinguish its coins, even after the various branch mints were created and their use of mintmarks was made law. The first time a “P” mintmark was placed on a coin from Philadelphia was in 1942 on the five cent coin, as part of a temporary design change meant to draw attention to the denomination’s wartime composition, which included silver.

The use of the “P” did not become standard until 1980, and even today its presence is not universal; cents struck at Philadelphia still lack mintmarks. For dates before then, it would be reasonable to assume that a coin without a mintmark was made there, but if the mintmark were missing from a die – by grease filling it in, for example, or a worker accidentally effacing it – how would anyone know? In fact, one such error, the 1922 “No D” cent, was identified solely because Philadelphia, for only the second time in its history, did not strike any cents that year. As for the number of undiscovered errors like it, collectors can only speculate.

At the other end of the spectrum are immediately apparent errors such as the 1990 “No S” cent. After proof coinage resumed following the hiatus from 1965 to 1967, it transferred from Philadelphia, where proofs were made without a mintmark, to San Francisco. As a result, the “S” mintmark became the norm on proofs, but the changeover was not without its hiccups. The first year of San Francisco proof coinage, 1968, saw a small percentage of the year’s dimes made from an obverse proof die that lacked the mintmark. A similar error occurred on a handful of dimes in three other years: 1970, 1975, and 1983. Nor was the problem restricted to dimes; a 1971 nickel die was blundered the same way, and 1990 added the “No S” cent to the mix.

Since those dimes, nickels, and cents were included in proof sets containing other coins with prominent “S” mintmarks, the missing-mintmark coins were easily spotted, and word spread quickly. Interestingly enough, since millions of proof sets were produced for each of those years, not all of those sets have been searched for missing-mintmark errors, and I can attest from personal experience that more of those errors are out there, waiting to be discovered. Perhaps that proof set Aunt Sally gave you for your birthday has an extra present waiting inside!

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-John Dale