The exchange rate

As I recall, at that time, the exchange rate between the Japanese yen and the U.S. dollar was 360 yen to the dollar.

The exchange rate between the Okinawan yen and the U.S. dollar was 120 yen to the dollar.

This suggests that the exchange rate between the Japanese yen and the Okinawan yen would have been three Japanese yen to one Okinawan yen.