1 Mon 'Wadōkaichin' old type, copper

The Wadōkaichin was Japan's first imperially minted coinage, authorized under Empress Genmei in 708 following the discovery of copper deposits in Musashi Province — the name itself translates roughly as "Japanese Copper Opening Treasure." The court modeled the coins closely on Tang Dynasty cash coins, part of a deliberate policy of administrative Sinicization that also produced the Taihō legal codes just years earlier.

Circulation was largely confined to the capital region. The government attempted to drive adoption by requiring tax payments in coin, with limited success outside the aristocracy.