The koban gold coin (not to be confused with koban meaning police box) was an Edo Period Japanese flat, thinly beaten coin, oval in shape.
|Koban gold coins, Sado Gold Mine Museum|
|Koban at Sado Gold Museum, Aikawa|
The Tokugawa currency gradually became debased over the centuries leading to inflation, which was one of the reasons the Tokugawa regime was in deep financial trouble by the time Commodore Perry arrived in 1853. The koban was replaced in the Meiji Period with the Yen based on Western standards.
Japanese ceramic maneki neko are often made holding a koban coin for luck and are called "Koban Maneki Neko."
See a video of Sado Gold Mine
Sado Gold Mine map