Bu Coin of Japan: Ansei Ichibugin & Samurai Era History

Illustrated Specimen Details: Bu

Example Specimen: 1 bu, 1859-1868 — Japan (Edo shogunate / Tokugawa shogunate)

The bu is a remarkable rectangular silver coin, a traditional form of "bar money" used in ancient Japan during the Edo period. This specific specimen was minted between 1859 and 1868, during the final years of the Tokugawa shogunate and the reign of Emperor Kōmei (the 121st Emperor of Japan). Known as the Ansei Ichibugin, it belongs to the Ansei era, a period named after a motto meaning "tranquil government".

The design of the 1 bu coin is strictly regulated and rich in symbolism. Both the obverse and reverse are framed by 20 delicate sakura flowers. The central vertical inscription 一 分 銀 clearly identifies the denomination as "1 bu of silver". To ensure trust in the currency, the coin features an incuse stamp 定 (Jo), which acted as a guarantee that the silver content matched the face value.

These coins were produced by the Ginza (Silver Mint), an officially sanctioned monopoly established in 1598 to supervise the minting of silver and the management of mines. The reverse also bears the name 是㘴 (Jōze), referring to the hereditary line of master mint-inspectors who oversaw the quality and weight of the silver bars.

1. JAPAN (17th-19th centuries): bu = 4 shu = 1/4 ryō

History and Evolution of the Japanese Bu

The bu (分) is a fundamental unit of the unique tri-metallic monetary system of Edo-period Japan (1603-1868). While most world currencies adopted round shapes early on, Japan maintained a tradition of rectangular "bar money" for its silver and gold denominations. The term bu translates to "part" or "fraction", reflecting its position as 1/4 of the larger ryō.

Gold and Silver Variants

In the early Edo period, bu coins were primarily struck in gold and were round. However, by the 19th century, the rectangular silver ichibugin (1 silver bu) became the most widely circulated and iconic form. Collectors also frequently encounter the nibukin (2 gold bu), which, despite its name, was often made of base metal with a gold wash during times of economic hardship for the Shogunate.

The Ginza and Monetary Control

The production of bu coins was a matter of high state importance. The Ginza was not just a mint; it was a powerful guild or regulatory agency that controlled every aspect of silver production in Japan. Every silver bu had to be inspected by the Jōze officials. This strict control was necessary because the bu was a fiduciary currency — its value was decreed by the Shogun's government rather than based solely on the market weight of the silver, which was a revolutionary concept at the time.

The End of an Era

The 1859-1868 issues, like the one illustrated above, represent the final chapter of Samurai-era coinage. Following the Meiji Restoration in 1868, Japan rapidly modernized and moved toward a decimal system based on the yen. The traditional rectangular bu, along with its smaller counterpart the shu, were phased out, making these silver bars highly prized historical artifacts that capture the essence of a disappearing feudal world.

Linguistic Roots

The character for bu (分) is a shared heritage across East Asia. It appears on Chinese fen, Korean fun, and Vietnamese phan. In all these cultures, it denotes a fractional part, illustrating the deep economic and linguistic ties that connected the trade routes of the Orient for centuries.