6th century BC. Group comprising: cast 'coins' or currency pieces in the form of a bifacial dolphin. Sear 1684.13.55 grams total. This unique type of coinage was cast in Olbia, in the Black Sea area of Thrace from the 5th to 3rd century BC; there are many varieties; the casting method employed was adopted by the Gallic Celts who originally came from this area; the dolphins were generally cast in a tree form connected by the tail, although some examples seem to have been cast individually.