3 Bu - Ansei Countermarked 8 Reales

When Japan was forced open to foreign trade by the Convention of Kanagawa in 1854, the Shogunate faced an immediate arbitrage crisis: Western merchants recognized that silver was undervalued relative to gold in Japan and began draining the country's gold reserves at a catastrophic rate. As a stopgap, the government countermarked foreign silver — primarily Mexican and other Spanish-colonial 8 reales pieces — with two oval punches certifying their acceptance at a fixed rate of 3 bu, roughly three-quarters of a Mexican dollar's face equivalent.

The arrangement lasted only a few years before the Shogunate was forced into deeper monetary reforms. Countermarked pieces were withdrawn as dedicated trade coinage replaced them, making circulated survivors with both punches intact considerably harder to locate than the raw host coins themselves.