The gold currency unit named Ryo comes under shakkanho system. The currency was in circulation before the Meiji era of Japan. Later, it got replaced by yen.
The image is of Koban coin. The Koban was an oval gold coin from the Edo Empire, Japan. Koban was equivalent to Ryo which is an early Japanese monetary unit.
Prior to this period, its economy was based on rice. Therefore, the standard unit of measure was the koku based on the amount of rice needed to feed one person for one year.
However, Portuguese traded with Japan by gold to rice. It was equal to three kokus of rice which later became the coin of choice in foreign trade.
During the Tensho Empire, one Ryo was equivalent to four koku of rice, or 1000 brass coins. A new series of coins was issued based on European currency systems and the koban was discontinued during Meiji restoration in 1868.
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