mint mark
造幣所記号 / mint-mark — Making
A small mark showing where a coin was made.
Pegasos Stater of CorinthCirca 400–375 BC
Gold stater of Philip IICirca 336–328 BC
Tetradrachm of AlexanderBC 336–323
Takes the form of a single letter, star, flower, etc. Even for the same coin from the same year, a different mark means it was made in a different city. It was also a system to trace which mint was responsible when defective coins were found.