1 Mon 'Kan'eitsūhō' NISUIEI, reverse 三 SAN

Kan'eitsūhō coinage was authorized in 1626 under the Tokugawa shogunate and became one of the longest-running monetary issues in Japanese history, remaining officially valid through the Meiji reforms of the 1870s. The reverse numeral 三 identifies this as a product of one of the provincial mints designated during the early Kan'ei period — a decentralized production system that resulted in considerable variation in flan quality and coin weight across mint sites. The shogunate tolerated this inconsistency for decades before tightening oversight mid-century.