Mint mark

A mint mark is a letter, symbol or an inscription on a coin indicating the mint where the coin was produced.

Mint marks were first developed to locate a problem. If a coin was underweight, or overweight, the mint mark would immediately tell where the coin was minted, and the problem could be located and fixed. Another problem which could occur would be a dishonest mint official debasing the coin, or putting less precious metal in the coin than specified. The first mint marks, called "Magistrate Marks" were developed by the Greeks, and named the Magistrate in charge of producing that coin. Debasing a coin, or otherwise tampering with it, was a very serious crime, often punishable by death in many civilizations. For example, in 1649, the directors of the Spanish colonial American Mint at Potosi, in what is today Bolivia, were condemned to death for seriously debasing the coinage. The initials of the assayer as well as the mint mark were immediate identifiers when the coins were inspected.

In some cases the symbols found in the field of ancient Greek coins indicated mints, not magistrates. DAs Alexander the Great conquered territories their mints struck coins with the types he used in Macedon but marked with a local symbol. For example, Rhodes struck coins with Alexander’s types marked with a rose, a local symbol previously used on its own coins

A reform of Diocletian made mint marks a regular feature of ancient Roman coinage. These mint marks were placed at the bottom of the reverse of the coin and contained three parts. The first part indicates that this was a coin with either SM for Sacra Moneta, M for Moneta, or P for Pecurnia. The second part was an abbreviation of the name of the mint such as ROM for Rome or LON for London. The final part indicated the workshop within the mint. The reform of Anastasius, which is the traditional dividing point between the coinage of the Roman and the Later Roman (a.k.a. Byzantine) empires, replaced the mint marks on gold coins by the inscription CONOB, meaning the pure standard of Constantinople, which was used by a variety of mints. Mint marks continued on copper coinage until the second half of the seventh century, however.

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