In the period of Keicho koban (a type of gold coin used in the Keicho era), the ichi mon (a currency unit of the Edo period) coin was the only type of Kanei tsuho (old copper coin) that was worth less than the ichibuban (ichibu was equivalent to 1 kan mon (1,000 mon) according to the official quotation).
慶長小判の時代は、一分判より低額のものは寛永通寳一文(通貨単位)銭しかなく、一分は公定相場で一貫文に相当する。