Oberon has four types of currency and the system is a base 10 system thus:
10 copper = 1 silver
10 silver = 1 gold
10 gold = 1 platinum
Most purchases are done in copper, flashing around silver ensures the attention of commonfolk, as does the showing of gold among the upper classes. Rarely will a commoner accrue many gold in their life and a platinum piece is more a tale of myth and legend than reality (except, perhaps, to the King and the exhorbitantly wealthy).