From a hoard found in Clazomenae, a number of "staters" (a standard measure) from the sixth century BC.
The central "lion and bull" one is thought to come from Lydia. This puts them with the first coins ever struck, the invention is thought to be Lydian. The material was a mixture of silver and gold, electrum. Enc. Britt.: The early electrum coinage consisted of small, thick, bean-shaped pieces, with a device stamped in relief on one side, the other being roughly impressed. Their intrinsic value fluctuated according to their gold and silver content; but the weight of the unit was fairly steady at about seven to eight grams, and the types stamped on them were the guarantee of authority.
See another of this type of coin at the Istanbul msueum: http://www4.pbase.com/update_image/39245371 (there is a link back).