 Hideyoshi unified Japan, and thus centralized most of the minting of large denomination silver and gold coins, effectively putting in place the basis of a unified currency system.Hideyoshi developed the large Ōban plate, also called the Tenshō Ōban (天正大判), in 1588, a predecessor to Tokugawa gold coinage.A common practice in that period was to melt gold into copper molds for convenience, derived from the sycee manufacturing method.