Mint marks are used on coins to indicate the physical location of the United States Mint facility that produced the coin. Some countries use multiple letters or symbols to indicate the production facility. On United States coins, the U.S. Mint has used none, one, or two letters to indicate the mint facility that produced the coin.
The location of the mint mark will vary depending upon the type of coin. It has been a tradition in the United States that coins minted at the Philadelphia, Pennsylvania facility do not carry a mint mark since this is the main production facility for the mint. However, there are some exceptions and changes to the tradition where the Philadelphia mint facility began using a "P" as a mint mark on coins.
Why Does the Mint Use Mint Marks?
When the United States Congress first authorized the production of coins in 1792, there was only one facility that produced coins located in Philadelphia, Pennsylvania. The law also dictated that a panel of inspectors (The Assay Committee) would inspect a sampling of coins from each mint facility once a year. They would check to make sure the coins were composed of the proper ratio of metals, the weight was within acceptable tolerances, and the diameter and thickness of the coin were correct.
In 1838, the United States Mint began opening branch facilities to help produce coins for a growing nation. If the assay committee detected a problem with one of the coins, knowing which mint facility produced the coin would be necessary. The essay committee would then launch an investigation into why the coins produced at that facility were not of the proper metallic content or weight.
The Philadelphia Mint Begins Using a "P" Mint Mark
In 1943 a large "P" was added to the reverse of the Jefferson nickel to indicate that the metal composition of this coin was different (35% silver, 56% copper, and 9% magnesium) than previously minted nickels (25% nickel and 75% copper). This change in metallic content continued on Jefferson nickels through 1945.
In 1979 the U.S. Mint broke tradition by placing a small "P" on the obverse of the Susan B. Anthony dollars minted in Philadelphia. In 1980 a "P" was added to all remaining United States coins minted in Philadelphia except for the Lincoln cent. This tradition of not placing a mint mark on Lincoln cents continued through 2016.
The mint added a mint mark ("P") to the 2017 Lincoln cents manufactured in Philadelphia to celebrate the 225th anniversary of the founding of the United States Mint. The mint did not publicly announce that this change would be made to celebrate The 225th anniversary of the United States mint. Instead, they let these coins quietly slip out into circulation and let coin collectors discover them on their own. The tradition of not having a mint mark on Lincoln pennies made at Philadelphia resumed with the production of 2018 dated Lincoln cents.
The Exception to the Rule
In 1986, The United States Mint began producing gold and silver bullion coins. These coins were specifically targeted towards the investment market for precious metals. The mint uses a distribution channel of wholesale dealers that buy the bullion coins in bulk quantities.
Since demand is difficult to predict and production processes are difficult to schedule, the four active United States mint facilities, Philadelphia, Denver, San Francisco, and West Point will produce bullion coins for investors. However, the bullion-quality coins do not have a mint mark on them regardless of where they are produced. Therefore, it is impossible to tell which mint facility produced an individual gold or silver bullion coin.
However, a numismatist in 2017 filed a Freedom of Information Act claim for the mint to release the list of serial numbers that are associated with particular mint locations. Therefore, the producing mint facility can be identified on an un-open case of bullion coins by the serial number markings on the outside.
As with any product from the United States Mint, collectors will want to add one to their collection. Therefore, to appeal to the coin collecting market, the mint produces several different examples of each bullion coin. These may include special burnished uncirculated strikes, proof, reverse proof, and enhanced uncirculated finishes. These coins will always carry the mint mark of the producing facility.
Mint Marks Used on United States Coins
The following table illustrates the mint marks used by the various mint locations in the United States:
|Name||Mint Mark||City, State||Dates of Operation||Notes|
|Philadelphia||None or P||Philadelphia, Pennsylvania||1793 - Present|
|Denver||D||Denver, Colorado||1906 - Present|
|San Francisco||S||San Francisco, California||1854 - Present|
|West Point||W||West Point, New York||1984 - Present|
|Charlotte||C||Charlotte, North Carolina||1838 - 1861||Minted gold coins only|
|Carson City||CC||Carson City, Nevada||1870 - 1893|
|Dahlonega||D||Dahlonega, Georgia||1838 - 1861||Minted gold coins only|
|New Orleans||O||New Orleans, Louisiana||1838 - 1909|