Look carefully at this 1975 Roosevelt dime manufactured at the San Francisco Mint. It was part of a set of coins sold to collectors by the US Mint in 1975. Where the arrow is pointing, there should be a letter, “S,” standing for San Francisco, called a mint mark. But that mint mark is missing. Out of 2,845,450 proof sets sold that year, only two dimes without that “S” mint mark are known, and more could be out there. This appears to be a mistake or manufacturing error by the Mint, though some have speculated that maybe someone on the inside caused it to happen on purpose. It is known as the 1975 No S Proof Roosevelt Dime. One sold at public auction by the prestigious firm of Stack’s Bowers in 2011 for $349,600.

SOLD AT AUCTION FOR $349,600. The arrow is pointing to the space where the mint mark “S” would ordinarily appear. (Photo courtesy Stack’s Bowers Auctions, 2011 Chicago Auction)

This is not something that you can expect to find in your pocket change. Proof coins sport a chromium-like brilliance and are subjected to a special manufacturing process that gives them more detail and, often, a startling cameo contrast between the frosted devices (the part that stands out, such as the portrait, lettering and date) and mirror-like fields (the background). On a proof coin, the coin’s metal disk, called a planchet, is punched or struck two or more times, which gives these coins their spectacular appearance. Ordinary coins that are made by the US Mint for the public to spend are called business strike coins.

U.S. Proof Sets from 2019 sold to collectors. These are not meant to be spent. (Photo courtesy U.S. Mint)

There were 585,673,900 business strike 1975 Roosevelt dimes without that “S” mint mark struck by the US Mint for people to spend. These ordinary-looking pocket change coins were manufactured in Philadelphia.

Don’t get excited if you find an ordinary, non-proof 1975 Roosevelt dime without the “S” mint mark in your pocket change. It’s very common and worth ten cents.

But if you have a stash of 1975 proof sets bought from the US mint in your safety deposit box, it’s worth looking through them to see if you have the rare “No S” dime. In fact, it’s probably worth looking at some other proof set years to see if you have some coins that were manufactured in San Francisco and are missing that “S” mint mark.

Surprisingly, very few people take the time to look at each coin when they have piles of proof sets. These sets have declined in value precipitously over the last several years, and interest in collecting them has waned.

Last year, a woman brought a suitcase of her grandmother’s US proof sets to my office, and after looking at several hundred sets, I discovered a 1983 set with a Roosevelt dime missing the “S” mint mark. Hundreds of these 1983 No S Proof Roosevelt Dimes are known to exist, and her coin was worth close to $600.

In 1990, the US Mint reported that it manufactured 3,555 proof Lincoln cents without the “S.” The 1990 No S Proof Lincoln Cent is worth $2,500 in Gem condition (Proof-65 is also known as “Gem Proof” on the one through seventy scale, where one is the lowest and 70 is the highest). But not a lot of these coins have been accounted for. There are still many hundred out there in 1990 proof sets waiting to be discovered.

There are some other proof coins missing the “S” mint mark that are valuable, too. Besides the years 1975, 1983 and 1990 just discussed, I also recommend looking carefully at US proof sets from years 1968, 1970 and 1971.

The 1971 No S Proof Jefferson Nickel is estimated to exist in a quantity somewhere in the hundreds. It has an $850 value in Gem Proof.

The 1968 No S Proof Roosevelt Dime is estimated to have a known dozen specimens extant. Its value as a Gem Proof is about $12,500.

The 1970 No S Roosevelt Dime is also estimated to have a known dozen specimens extant. Its value as a Gem Proof is $650.

A reputable coin dealer can help you to identify and confirm the authenticity of your proof “No S” coins. Consult a dealership that is an authorized dealer and submission center for the Numismatic Guaranty Corporation or Professional Coin Grading Service.