A really choice representation of this fascinating coinage of Japan. While PCGS does note tooling, it has been done very sparingly and really has no impact on the visual impact of this super rare issue. A real prize for the specialist of Japanese gold coinage from this period. 

The Koban was a form of gold coinage used in Japan during the Edo period (1603–1868). It was introduced by Tokugawa Ieyasu, the founder of the Tokugawa shogunate, to standardize and stabilize the country's currency system. The name "Koban" literally means "small plate" in Japanese, reflecting the shape and design of the coin.

Key features of the Koban coinage:

1. Shape and Design: The Koban had a rectangular shape, resembling a small gold bar or ingot. The front side typically featured a stamped design, while the reverse was often left plain.
2. Gold Content: The Koban was made of gold, and its value was based on its weight. The gold content varied, but Koban coins were generally of high purity.
3. Denominations: Koban coins came in different denominations, and their sizes were standardized. The most common denominations were the Ichibukin (one Bu Koban) and the Ryo Koban. The Ichibukin weighed one Bu (about 3.75 grams), and the Ryo Koban was larger, weighing four times the Ichibukin.
4. Government Seal: Koban coins were stamped with the government seal to verify their authenticity. The seal usually included the shogun's family crest.
5. Monetary System: The Koban was part of a broader monetary system that included silver coins called "Ichibu Gin" and smaller denominations like Shu and Bu. The goal was to create a stable and standardized currency system.
6. Role in the Economy: The Koban played a crucial role in facilitating trade and commerce during the Edo period. It became a widely accepted form of currency, and merchants and samurai used Koban coins for transactions.
7. Limited Circulation: While Koban coins were in circulation, their use was not as widespread among the common people. The lower denominations and copper coins were more commonly used in everyday transactions.
8. End of the Koban System: The Koban system continued until the end of the Edo period in 1868. With the Meiji Restoration, Japan underwent significant political and economic changes, leading to the adoption of a modernized currency system.

The Koban is a fascinating aspect of Japan's monetary history, reflecting the economic policies and stability sought during the Edo period. Today, Koban coins are highly collectible and are often sought after by numismatists interested in Japanese history and culture.