1 Ryō 'Tenpō Koban'

The Tenpō Koban was issued in direct response to a fiscal crisis: the Shogunate had debased its gold coinage repeatedly since the early 18th century, and by the 1830s the Edo Kinza was producing kobans at dramatically reduced gold content compared to the Keichō standard of 1601. The Tenpō issue was not a reform but a continuation of that debasement — fineness had fallen from roughly 84% at inception to the .568 recorded here.

Production ended not by design but by political collapse. The arrival of Perry's fleet in 1853 triggered currency chaos, and the exchange rate between Japanese and foreign silver exposed the koban's overvalued gold content to immediate arbitrage exploitation.