1 Mon 'Nyōyakushinpō'

The Jōgan Eirihō, struck between 859 and 870 under Emperor Seiwa, was the fifth of Japan's Twelve Ancient Coins — the Kōchōjūnisen — issued by the Ritsuryō state in its attempts to establish a functioning copper coin economy. That project was failing by this point. Peasants hoarded coins, court officials accepted them only under compulsion, and the government repeatedly had to mandate their use by law. The Nyōyakushinpō is among the later, increasingly debased issues in that sequence, and official minting effectively collapsed within decades of this coin's production.