Yogin (洋銀)
Yogin is a foreign silver brought in to Japan at the end of the Edo Period through the beginning of the Meiji Period. In most cases unless otherwise specified, Yogin refers to the so-called Spanish dollar, 8 real silver coin of 420 grains of weight, which was coined in Mexico (then-Spanish colony) and other Central and South American countries of Spanish origins and had long been used in international settlement since 1497.
Since the Ansei Treaty had been signed, foreign merchants were allowed to buy Japanese goods with foreign silver coins, and their exchange rate at that time was 311 ichibu-gin silver coins against 100 Spanish dollar. However, the Tempo ichibu-gin silver coin was nominal money in that its face value was set higher than its bare metal value, but the grade of the silver coin was still higher than that of Spanish dollar. Therefore, much higher-valued koban gold coins exchangeable to the ichibu-gin coins (four ichibu-gin silver coins for one koban gold coin) was drained out in massive amount. For this reason, large amount of Spanish dollars flooded into Japan and were used for minting silver coins during the Meiji Period.
In 1859, the Edo bakufu feudal government set an regulation that one Spanish dollar should be equivalent to sanbu-kin gold coins, and on February 20, 1868, the Meiji government also established a rule following this. In 1871, the New Currency Act was enacted and on May 27, 1878, the edict of Dajokan (Grand Council of state) was issued to coin silver trade dollars in Japan equivalent to Spanish dollars and use the trade dollar as one-yen silver coin across the nation, and on September 12, the following year, the gold and silver standard system was declared to allow the use of Spanish dollars and silver trade dollars in accordance with the exchange rate set between the both governments (gold and silver bimetallism).
The ichibu-gin silver coins disappeared after the rearrangement of paper money and the issuance of convertible currency, and in concurrence with the transition to the gold standard system in 1897, the distribution of the one-yen silver coin was halted in Japan and the value of the Spanish dollars dropped significantly in Japan.