The image on this drachma from Istria is unexplained. Maybe the two juvenile heads symbolize the commercial activities of Istros downstream and upstream. Or they allude to sunrise and sunset – i.e. the coming and going of the sun god, whose worship had been adopted from Miletus by the Istrians: Miletus was the city, which had founded Istria sometime between 650 and 600 BC. Perhaps the two youths depict the twins Castor and Pollux, who where considered the patrons of navigation.
The reverse of the coin shows a white-tailed eagle seizing a dolphin. The eagle is Zeus, lord over life and death. The dolphin stands for the safe passage of ships and for maritime trade. That the dolphin loses his life in the clutches of an eagle illustrates the helplessness of any creature before the gods.