 The material for the coinage came from gold and silver mines across Japan.For this purpose, new gold mines were opened, such as the Sado and Toi gold mines in the Izu Peninsula.Regarding diamond coins, the "Kan'ei Tsūhō" coin (寛永通宝) came to replace the Chinese coins that had been in circulation in Japan, as well as those that were privately minted, and became the legal tender for small denominations.