A koban is a traditional Japanese oval gold coin that was used during the Edo period (1603-1868). It typically weighed about 1 ryo, which was a unit of currency at the time. Koban coins were often stamped with intricate designs, including the Tokugawa family crest, and were considered a symbol of wealth and prosperity. Koban coins played a significant role in Japan's economy, facilitating trade and commerce. They were often used in large transactions and were highly valued for their gold content. Today, koban are sought after by collectors and historians for their historical significance and artistic craftsmanship.