Coins have been used as a form of currency across the world for almost three thousand years. Much like today, the earliest coins were formed from metals, with more precious metals reflecting higher monetary value. The most common shape of coin is flat, rounded disc shape, which also tends to be small in size. Antique and rare coins can hold high value on the collectors’ market, and some coins produced by Greece can be of particular interest to numismatists. Archaic Greece was one of the first nations to develop coins around the 7th century BC, resulting in a rich numismatic history. During the Classical period, Greek coins began to demonstrate outstanding technical skill, with coins being produced bearing detailed portraits and images. The images on these coins varied by region; for instance, the drachmas of Athens paid tribute to the city's goddess, Athena, through the depiction of an owl.