http://agathe.gr/democracy/athenian_currency.html
Athenian Currency Many of the specialized administrative boards have left material traces of their activities. Most prolific of these were the moneyers, or Overseers of the Mint. Throughout her history ... The building identified as the Mint is a large rectangular structure, over 25 meters long on one side and, in addition to the coin blanks, it produced evidence of industrial activity such as furnaces and large water basins. It cannot have been the only mint used by the Athenians as it dates to 400 B.C., far too late for much Athenian coinage, and analysis of the industrial debris indicates that only bronze and no silver was worked in the building.