4 Mon 'Kan'eitsūhō' Meiwa Copper Alloy, 11 waves

The Kan'eitsūhō series had been minted in various forms since 1636, but the four-mon copper issues introduced under the Meiwa era represented a deliberate government response to chronic small-denomination shortages that had plagued the Tokugawa economy for decades. The eleven-wave reverse — distinguishing this type from the seven-wave variant — was a design decision tied to mint attribution and period of issue, not aesthetics.

By the 1770s, widespread counterfeiting of these coins had become a serious administrative problem for the Edo shogunate.