The ordinary silver coinage of Athens from B.C. 480 to 400 is almost unvaried. By the former date a head of Athena and an owl of fixed and conventional archaic type had been adopted for the coin (Pl. XIII. 1). The olive-wreath which adorns the helmet of the goddess seems to have been adopted during the glow of triumph after Marathon. At the end of the century there were certain issues of gold coins, of which we shall speak later. But the great mass of the coinage was in silver. The Athenians obtained silver in abundance from the mines of Laurium and those of Thrace, and it was part of Athenian policy to circulate the coins as widely as possible, and to make them the standard currency of the Aegean. Silver was to Athens what gold was to Persia, the backbone of the finance of the state, and, together of course with the tribute of the allies, the source whence came the plentiful wealth which Athens used for great building-works at home and for expeditions abroad.