A mint mark is any feature embedded in a coin to indicate where it was produced. Mint marks are important in collecting because collectors tend to treat coins stuck at different mints as distinct coins, even if they were minted with the same design and date. The price of a coin will reflect this distinction. For example a United States 1913 "Buffalo" Nickel struck at the Philadelphia Mint could probably be found in extremely fine condition for about $20. That same 1913 nickel struck at the San Francisco Mint would cost you closer to $600 in the same condition. The reason for this price spread is simple. There were almost 30 million nickels struck in Philadelphia that year compared to about 1.2 million in San Francisco.
Mint marks were first introduced by the ancient Greeks where they were called Magistrate Marks. Their primary function has always been as a quality control tool, to help identify the source of problem coins in circulation. Issuing authorities have an obvious interest in chasing down underweight, overweight and poorly struck coins, as well as coins that have fraudulently been struck with a lower precious metal content than indicated.
Throughout history mint marks have taken many forms. Some marks are large and prominently placed; others are so small and discrete they are difficult to observe without magnification. The most straightforward mark simply names the mint, but this practice has not been very common. Frequently marks are made up of one or several letters. These letters might be an abbreviation of the mint, such as S for San Francisco, or they might be a code for that mint, such as K for Bordeaux on 19th century French coins. Other marks use an iconic symbol known as a Privy Mark to indicate the mint, such as the Royal Canadian Maple Leaf.
1918 British Sovereign with P mint mark indicating Perth, Australia. Beginning in 1871 Britain began striking sovereigns at branch mints, closer to the source of mined gold and closer to where currency was needed in circulation. Sovereigns were struck at Perth from 1899 to 1931. Some Perth Sovereigns are scarce.
360-363 AD Roman Julian II with the legend NIKB between branches NIK indicating the Nicomedia Mint and B indicating the second workshop. Roman mints began using mint marks at about the 3rd century AD.
315-311 BC Alexander III 'The Great' Tetradrachm struck at the Babylon mint. During his reign, 336-323 BC, Alexander established an enormous empire that at one point extended from the Adriatic Sea to the Indus River and encompassed all of Persia. He issued a great deal of coinage to fund his conquests which became the standard of the day and was produced for centuries after his death at mints throughout the ancient world. Mint marks on the reverse of this tetradrachm include the MP monogram in a wreath and the monogram below throne between the legs.
1855 French Napoleon III ten centimes. The B mint mark indicates the Rouen mint. The coin also features the dog's head privy mark of Jean-Jacques Barre, Engraver General 1843-55, and the pick and shovel is the Mint Director's mark used at Rouen 1853-57.
1878 U.S. Morgan Dollar Reverse showing the CC mint mark for Carson City. The Carson City Mint is legendary among collectors of United States coins. It was established to be near silver being mined after the discovery of the Comstock Lode. The mint was only in operation between 1870-1893 and produced some of the United States' great rarities.
1915 German Empire five pfennig with an F mint mark indicating the Stuttgart Mint. The unified German Empire minted coins featuring the Imperial Coat of Arms from 1871 to 1918. Other German mints operating at the time included Berlin (A), Munich (D), Muldenhutten (E), Karlsruhe (G), and Hamburg (J).
1881 Mexican silver ten centavos. The Ho marking indicates the Hermosillo mint which operated from 1832 until 1895 in the Mexican State of Sonora. The A is the mark of assayer Jesus Acosta. The number 902,7 attests to the purity of the silver in the coin - in this case 902.7 parts per thousand, or 90.27%.
1913 Russia silver twenty kopek. The mint mark СПБ is in Cyrillic and was used on coins struck at the Saint Petersburg Mint between 1724-1914. The Cyrillic characters ВС are the mint official's initials, Victor Smirnov, who presided at Saint Petersburg between 1913-1917.
1811 Peru eight reales. Although at first glance the mint mark appears as ME, it is actually a monogram of the letters LIMAE to indicate the Lima Mint. JP are the assayer's initials.