"In pre-Islamic Arabia, the Byzantine gold dinar, Persian silver dirhami, and copper fals (or fels; pl. falus or fulus) were used as coins. The value of both dinar and dirham was determined by their metal content (but not the fals). Coinage was not issued by a government authority, and minting coins was in the hands of private individuals. Disputes regarding weight and quality caused loss of economic efficiency; it did, however, provide competition and thus consumer choice. In the early Islamic Empire, Muslims continued to use Byzantine coins, but over time they outlawed the use of these coins and centralized the production of an Islamic dinar and dirham."

- Islam Economics

Sounds familiar, right?