Japanese Empire, Edo Period, Shogun Tokugawa Ienari, Kobankin

The first kobans were issued in Japan around 1600. They were large oval gold coins with a value of 1 ryo, a unit of weight of about 18 grams (0.63 ounces). During the 260 years of their circulation, the kobans lost weight significantly, however; this piece from the 1820s weighs only about 13 grams (0.46 ounces). Kobans were very valuable coins: one koban held 4,000 copper coins. Of course these amounts of copper coins were not counted but chained on strings in numbers of 100, 500 or 1,000. Or they were just weighed – one koban equaled 7.5 kilograms of copper coins.