1 Ryō 'Genbun Koban' reverse regular 文 BUN

The Genbun Koban was struck from 1736 following a deliberate debasement ordered by Senior Councillor Matsudaira Norimura, reducing gold fineness sharply from the preceding Kyōhō Koban. The Tokugawa treasury was under sustained fiscal pressure, and the recoinage — melting down higher-purity coins to strike more numerous lower-purity ones — generated immediate profit for the bakufu while quietly eroding the currency. It remained in production for over eighty years, one of the longest runs of any koban type.

The "regular 文" designation distinguishes standard reverse stamps from rarer certified variants. Issued across the tenures of four shoguns.