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

The Kan'eitsūhō series had been produced, with interruptions, since 1636 — but the Bunsei-era 4 mon issues emerged from a specific fiscal squeeze, as the Shogunate sought to stretch copper supplies while maintaining nominally higher-value circulation pieces. The "11 waves" designation distinguishes this variety from related dies by the wave count on the reverse, a detail cataloguers use to separate what were, to most Edo-period merchants, functionally identical coins.

Bunsei copper issues are frequently found with uneven casting surfaces, a consequence of declining quality control at the Edo and Osaka casting sites during the 1820s.