Never change a winning team! This might be the reason why the Ionian town of Phocaea imperturbably minted electron coins till the 4th century BC. The Persian Empire and the other Greek towns had been using silver and gold for coinage for a long time in those days. But then, why change what has proved its worth? After all the Phocaean coins were willingly accepted by all the city's trading partners, and were circulating far and wide.