1 Ryō 'Bunsei Koban' Reverse grass script 文

The Bunsei Koban was authorized following the Shogunate's attempt to stabilize gold coinage after decades of debasement cycles stretching back to the Genroku era. The Kinza, Japan's state gold mint operating under strict hereditary monopoly held by the Gotō family, produced koban using hand-finishing techniques that introduced subtle variation between individual pieces. The grass-script 文 kakihan on the reverse is the authenticating seal of the sitting Gotō head — a personal cipher, not a decorative choice.

At .559 fineness, this is notably debased relative to the Keichō koban's original standard of roughly .857. That reduction accumulated across seven prior reissues spanning nearly two centuries.