US Mint Marks Explained

Why the Mint started adding mint marks

For its first 45 years the United States had one mint, in Philadelphia, so no coin needed to say where it was made. That changed with the Act of March 3, 1835, which created three branch mints: New Orleans in Louisiana, Charlotte in North Carolina and Dahlonega in Georgia. All three opened for coinage in 1838. Once more than one facility was striking the same coins, the Treasury needed a way to trace any coin that came up short in weight or fineness back to the officers who made it. A small letter on the die was the simplest answer.

The annual Assay Commission, which met in Philadelphia to test sample coins from every mint, relied on those letters. Branch coiners knew their work could be identified, which gave them a strong reason to keep standards high. Collectors inherited the system almost by accident. A mint mark that was added for accountability now tells you whether a coin came from a mint that struck millions of pieces or one that struck a few thousand.

How the branch mints followed the gold and silver

Nearly every branch mint was built close to a source of precious metal. Charlotte and Dahlonega served the gold fields of the southern Appalachians, where miners otherwise had to ship raw gold hundreds of miles to Philadelphia. New Orleans handled gold and silver arriving through the busiest port in the South. San Francisco opened in 1854 to turn California Gold Rush dust into coins. Carson City followed in 1870 to coin silver from Nevada's Comstock Lode. Denver began as an assay office in 1863, when the government bought the private Clark, Gruber and Company mint, but it did not strike coins until 1906.

The Civil War closed all three southern branches in 1861. Charlotte and Dahlonega never struck coins again. New Orleans reopened in 1879 and worked until 1909. Carson City shut its coining department in 1893 as silver lost its political support. By the early twentieth century the system had settled into the pattern collectors know: Philadelphia, Denver and San Francisco. West Point, opened in 1938 as a bullion depository, struck its first coin with a W in 1984 and received full mint status in 1988, the same year San Francisco regained its own status as a mint.

Every US mint mark letter in one place

P or no letter means Philadelphia. D means Denver from 1906 onward but Dahlonega on gold coins dated 1838 to 1861. S is San Francisco, O is New Orleans, CC is Carson City, W is West Point and C is Charlotte. Because Denver and Dahlonega share a letter, the date and the metal settle any doubt: no Denver coin is older than 1906 and no Dahlonega coin is younger than 1861.

A missing letter does not always mean Philadelphia. No US coin dated 1965, 1966 or 1967 carries a mint mark, because the Coinage Act of 1965 removed them to discourage hoarding during the silver shortage. From the 1970s into the 1980s West Point also struck millions of cents and some quarters with no letter, so those coins are indistinguishable from Philadelphia pieces. The P itself is a latecomer. It first appeared on the 1942 to 1945 silver war nickels, returned on the 1979 Susan B. Anthony dollar and spread to every denomination except the cent in 1980. Cents carried a P only in 2017.

Where mint marks moved over the years

On most nineteenth century silver the mint mark sat on the reverse, usually below the eagle or the wreath. The early New Orleans half dollars of 1838 and 1839 are an exception, with the O placed above the date on the obverse. Gold coins carried the mark on the reverse near the eagle or below the wreath. Lincoln cents broke the pattern in 1909 by placing the letter on the obverse below the date, where it has stayed.

When mint marks returned in 1968, the Mint moved them to the obverse on every denomination. Jefferson nickels moved theirs from beside Monticello to below the date, Roosevelt dimes from the base of the torch to above the date, Washington quarters from below the eagle to behind the ribbon and Kennedy halves from the reverse to below the bust. If you are checking a coin from before 1965, look on the back first. For anything from 1968 on, look on the front.

How mint marks were put on the dies

For most of the Mint's history each working die received its mint mark by hand. An engraver placed a small steel punch on the die and struck it with a hammer, which is why the same letter can sit in slightly different positions from one die to the next. When the punch bounced or was struck twice, the result was a repunched mint mark, such as a D sitting over another D. Occasionally a die meant for one mint was repunched with another letter, creating over mint marks like D over S.

The Mint began putting the mint mark on the master die for proof coins in the mid-1980s and for circulation coins in the early 1990s, which ended most repunched mint mark varieties. A modern coin with a missing or doubled letter is therefore far rarer than a similar coin from the 1940s or 1950s.

Checking that a mint mark is genuine

Because one letter can turn a common coin into a key date, mint marks are a favorite target for alteration. Forgers add a D to a 1914 Philadelphia cent or a 1916 Philadelphia Mercury dime, or an S to a 1909 VDB cent. They also remove letters to imitate Philadelphia rarities. Under magnification a genuine mint mark has the same luster and wear as the field around it and blends into the surface at its base. An added letter often shows a seam, glue, tool marks or a different color. Every key date mint mark has a known shape and position, so comparing your coin with an authenticated example is the best single check.

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