4 Mon 'Bunkyūeihō' Bosen, tin alloy, cursive script, KŌKAKU KATSUEN

The Bunkyu Eiho 4 mon pieces in tin were trial issues — pattern coins, not circulating currency — produced as the Tokugawa shogunate experimented with alternative compositions during a period of acute copper shortages. The Kōkaku Katsuen attribution identifies the specific casting authority, a detail that matters for provenance within a series where multiple foundries produced nearly indistinguishable types. Tin was ultimately rejected for general circulation, making the surviving examples products of administrative deliberation rather than monetary deployment.