Here is a link to a dealer in Malaysia that who has a silver isshu gin (1 shu) bar. These were produced around the end of the Tokugawa Shogunate in Japan (1853-1865).

Regarding the monetary units, this is from Wikipedia:

The mon (文) was a currency of Japan from the Muromachi period in 1336, until 1870. The Chinese character for mon is 文 and the character for currency was widely used in the Chinese-character cultural sphere, eg. Chinese wen and Korean mun. Coins denominated in mon were cast in copper or iron and circulated alongside silver and gold ingots denominated in shu, bu and ryō, with 16 shu = 4 bu = 1 ryo. The yen replaced these denominations in 1870. However, its usage continued at least into 1871, as the first Japanese stamps, issued in that year, were denominated in mon.