A Mint mark on a United States coin is a small letter (or letters) placed on the field (the flat, featureless areas surrounding the designs and lettering) of the coin to show which Mint manufactured it. Mint marks have been used for almost as long as coins have been struck.

Listing of Mint marks

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History of Mint marks
From 1793 to 1838, the only U.S. Mint in operation was located at Philadelphia, thus there was no need to distinguish it by a Mint mark. That changed when three Branch Mints were authorized by the Act of March 3, 1835: In Charlotte, N.C.; Dahlonega, Ga.; and New Orleans, La.

In order to distinguish which Mint struck a particular coin, Mint marks were introduced on coins struck at the Branch Mints. The Philadelphia Mint, however, continued to strike coins without Mint marks.

As new Branch Mints were authorized and opened, new Mint marks were introduced. There have been eight different Mint marks used since the United States began striking coins in 1792 (see the accompanying chart).

With one four-year exception, U.S. coins struck at the Philadelphia Mint bore no Mint marks until 1979. A "P" Mint mark was used on the Jefferson, Wartime 5-cent coins, struck from 1942 to 1945 in a silver alloy. The "P" Mint mark on these issues was designed to distinguish the silver alloy issues from regular copper-nickel 5-cent coins.

In most cases, the Mint marks were applied to the reverse sides of U.S. coins until 1968. There are a few exceptions, however, including 1838-O Capped Bust half dollars and 1916-D and 1916-S Walking Liberty half dollars.

Mint marks have not always been used used, even at the Branch Mints. The Coinage Act of 1965, which authorized the replacement of silver coinage with copper-nickel clad coinage, also approved the dropping of Mint marks. Mint marks were not used on coins dated 1965 through 1967. The move was designed to help alleviate a coin shortage by removing the distinction between coins struck at Branch Mints and those struck in Philadelphia so collectors could not determine which were the more limited strikes.

With the announcement Jan. 4, 1968, that Mint marks would return to coins, Mint Director Eva Adams made a major change in Mint mark application. To achieve uniformity, she directed that all Mint marks be placed on the obverse. She continued the practice of not placing Mint marks on coins struck at the Philadelphia Mint.

A coining facility was opened at the West Point Silver Bullion Depository in 1975, initially to strike cents (and in later years, quarter dollars). These coins are indistinguishable from Philadelphia Mint coins, since they bear no Mint mark.

At the same time (mid-1970s into the 1980s), some coins struck at the San Francisco Assay Office were produced without Mint marks, primarily to prevent collectors from hoarding the S-Mint coins.

Major changes were made in Mint mark policy beginning in 1979. Anthony dollars struck at the Philadelphia Mint were given a P Mint mark. The list of coins to bear the "P" Mint mark grew in 1980, when all other Philadelphia denominations but the 1-cent coin received the new Mint mark.

A new Mint mark, "W," was belatedly established in September 1983, when the West Point Bullion Depository (now the West Point Mint) began striking 1984-dated $10 gold eagles commemorating the Los Angeles Olympic Games. As noted, the West Point facility had been striking coins for circulation without Mint marks. Production of circulating coinage (strictly cents by this time) at West Point continued without the addition of a W Mint mark.

The W Mint mark has been used on various commemorative and bullion coins since then, as well as a 1996-W Roosevelt dime included in the 1996 Uncirculated Mint set as a commemoration of the 50th anniversary of the design. However, no coins struck for circulation have born a W Mint mark.

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Why are Mint marks important?
Collectors determine a coin's value by examining its date, Mint mark and condition. The most important criterion in determining a coin's value is its condition. However, determining the Mint that struck the coin is extremely important in arriving at its value. That's because the coin may be struck in large quantities at one Mint and very small quantities at another. Consider the 1914 and 1914-D Lincoln cents: more than 75 million examples were struck at Philadelphia (with no Mint mark) but only 1.193 million have a little D mark below its date.

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Mint marks today
Let's examine our current pocket change or coins that collectors may find in today's circulating coinage.

Lincoln cents, 1909-96, have used two Mint marks (but have been struck at four Mints). Collectors will find a little "D" for the Denver Mint or "S" for the San Francisco Mint, located directly beneath the date.

Jefferson 5-cent coins, 1938-96, have used three Mint marks, in three different locations. Denver and San Francisco coins struck from 1938-42, and from 1946-64, feature the D or S on the reverse, to the right of the representation of Monticello. The Mint marks were enlarged and moved to above the dome of Monticello on the wartime alloy coins of 1942-45, and as noted, a P Mint mark was used for the first time. The D and S Mint marks have appeared on the obverse, just below the last numeral of the date, since 1968, and the P Mint mark has appeared in the same location since 1980.

Roosevelt dimes, 1946-96, have used four Mint marks since their introduction. The Denver and San Francisco dimes of 1946-64 bear a D or S Mint mark on the reverse, to the lower left of the torch. The Mint mark was moved to the obverse in 1968, to just above the last numeral in the date, where it remains today. The P was added in 1980, and the W was used on special 1996-W dimes sold to collectors.

Washington quarter dollars, 1932-96, have used three Mint marks. Denver and San Francisco quarters struck from 1932-64 bear the D or S Mint mark on the reverse, between the wreath and the denomination QUARTER DOLLAR. The Mint marks were moved to the obverse in 1968, to behind Washington's queue. The P was added in 1980.

Kennedy half dollars, 1964-96, have used three Mint marks. A D Mint mark was used on the reverse of Denver Mint coins in 1964, just above the L in HALF. It's the only such Kennedy half dollar to bear a Mint mark on the reverse. The D and S Mint marks were moved to the obverse in 1968, right below the bust of Kennedy and above the date on the obverse side of the coin. The P was added in 1980.