The meaning of the stand-alone letters on a U.S. coin is not always clear. Different coins have different letters and inscriptions on them, but virtually all the obscure letter combinations on U.S. coins refer to either the initials of the designer of the coin or the place where the coin was minted.
The initials of the coin designer are placed somewhere on most U.S. coins. These initials are generally two or three letters long and they are usually very small. A magnifying glass is sometimes required to read the initials accurately. For an example of the designer's initials being engraved on a coin, look no further than a common dime. Beneath Roosevelt's neck, just right of the center of the coin, there are two extremely small letters, "J S." These stand for John Sinnock, the designer of the Roosevelt dime.
Active Mint Marks
Four mints are producing U.S. coins as of 2011. Two of these mints, San Francisco, California (S) and West Point, New York (W), only produce special issue coins such as proof sets and bullion coins. All of the circulating coins produced each year come from either the Philadelphia, Pennsylvania mint (P) or the Denver, Colorado mint (D). Not all coins minted in Philadelphia carry a mint mark, so if you cannot find a mint mark anywhere on either of the coin's faces, it was likely minted in Philadelphia.
Historic Mint Marks
Four other mints were used to produce coins throughout the history of the United States. The Charlotte, North Carolina (C) and Dahlonega, Georgia (D) mints only produced gold coins during the mid 19th century. The Denver mint did not produce gold coins, so it is possible to tell the difference between the Denver and the Dahlonega mint simply by looking at the composition of the coin. The New Orleans, Louisiana (O) and Carson City, Nevada (CC) mints both produced circulating silver and gold coins.
Other Words and Letters
Most U.S. coins contain the easy-to-understand words "United States of America," "Liberty" and "In God We Trust," along with a declaration of their value. The majority of U.S. coins, however, do have the inscription "E Pluribus Unum" on one of their faces. This is one of the Nation's mottoes, and is Latin for "Out of Many, One."