The tetradrachm was the first trade coin of the world. The owls, as they were called in vernacular on account of their never-changing image, were minted from the end of the 6th to the end of the 1st century BC (510-38 BC). During all that time the design remained unchanged. The owl was the attribute of the city goddess Athena, the goddess of wisdom.
Athena was a special case among antique deities as she was the only goddess who was the emblem on the coins of two cities. The competing trade towns of Athens and Corinth both introduced Athena's head on their money at the end of the 6th century BC. To distinguish the coins of the two towns, the goddess was depicted with different helmets: On coins from Athens she wore an Attic helmet, and on those of Corinth a Corinthian one.