There is obscurity about the production of the precious metals in old Japan. That gold, silver, and copper were known and used is certain, for in the dolmens,--which ceased to be built from about the close of the sixth century (A.D.)--copper ear-rings plated with gold are found, and gold-copper images of Buddha were made in the reign of the Empress Suiko (605), while history says that silver was discovered in the island of Tsushima in the second year of the Emperor Temmu's reign (674). From the same island, gold also is recorded to have come in 701, but in the case of the yellow and the white metal alike, the supply obtained was insignificant, and indeed modern historians are disposed to doubt whether the alleged Tsushima gold was not in reality brought from Korea via that island. On the whole, the evidence tends to show that, during the first seven centuries of the Christian era, Japan relied on Korea mainly, and on China partially, for her supply of the precious metals. Yet neither gold, silver, nor copper coins seem to have been in anything like general use until the Wado era (708-715). Coined money had already been a feature of Chinese civilization since the fourth century before Christ, and when Japan began to take models from her great neighbour during the Sui and Tang dynasties, she cannot have failed to appreciate the advantages of artificial media of exchange. The annals allege that in A.D. 677 the first mint was established, and that in 683 an ordinance prescribed that the silver coins struck there should be superseded by copper. But this rule did not remain long in force, nor have there survived any coins, whether of silver or of copper, certainly identifiable as antecedent to the Wado era. It was in the year of the Empress Gemmyo's accession (708) that deposits of copper were found in the Chichibu district of Musashi province, and the event seemed sufficiently important to call for a change of year-name to Wado (refined copper). Thenceforth, coins of copper--or more correctly, bronze--were regularly minted and gradually took the place of rice or cotton cloth as units of value.