The first Greek coins were minted in Aegina from 560 BCE, and then Athens and Corinth also began their own coin production shortly after. Each city used an easily identifiable symbol: a turtle for Aegina, an owl for Athens and a winged-horse for Corinth. The turtle was an apt choice for the Mediterranean trading power, the owl was associated with Athens’ patron goddess Athena, and Pegasus was the horse of the Corinthian hero Bellerophon. Other cities soon produced their own coins and images from Greek mythology continued to be popular in coin designs. Later, letters and short inscriptions were added to signify the issuing authority. The coins were created by hammering a plain metal disk placed between two engraved metal dies made from hardened bronze or iron. The disks were heated first to aid the stamping of the design. Greek coins were most commonly made of silver, gold, or a copper alloy.