1 Mon 'Kayūtsūhō' Regular Script

Cast in Nagasaki under shogunate license, these coins were produced to address a chronic shortage of small-denomination copper currency in the city's active trading port. The Kayūtsūhō series takes its name from the Chinese characters used in their casting — a deliberate nod to the Sino-Japanese commercial networks that made Nagasaki, as Japan's sole sanctioned foreign trade port under the sakoku edicts, the country's most monetarily complex city.

The regular script variant is distinguished from the cursive Gyōsho type by stroke form alone — a distinction that occupied Japanese numismatists considerably more than it did the merchants spending them.