Japan has a long numismatic history which dates back to when coins were first introduced from neighboring Korea and China. It is not known exactly when the first imports occurred, but it may have been even earlier that the first century A.D. What we know for certain is that following the establishment of diplomatic relations with the T’ang of China, Japan imported T’ang coins, the first of which was the Kaigen Tsuho in 618 AD.

The next phase of coin use was in the early eighth century when Japan introduced its own mint. This mint came about when a large deposit of copper was found in Musashi province. Copper was discovered in the Chichibu District of what is now Saitama Prefecture, and the Japanese were so delighted with the discovery that they named the Wado era (708 A.D. – 715 A.D.) after it. Wado means “Japanese Copper” and the first coin that was minted was the Wado Kaiho, or Wado Kaichin, in 708 A.D.

The Wado Kaiho was modeled after the Kaigen Tsuho (K’ai Yuan T’ung Pao in Chinese), and whilst the majority were cast in copper, a few were also cast in silver. The Japanese and Chinese coins are very similar, however, the Wado Kaiho is read clockwise starting from the top, whereas the Kaigen Tsuho is read top-bottom, right-left.

The Wado Kaiho has two distinct varieties. The first batch were rather poor quality, and the second batch improved greatly after experts from the Chinese mint were called over to offer advice on the minting process.

Over 250 years from 708 A.D. to 958 A.D. the Japanese minted 12 coins. In addition to copper coins there was the Kaiki Shoho, which was gold, and the Taihei Genpo, which was silver. These are very rare coins, with the only known Kaiki Shoho in the Tokyo National Museum. Overall the coins declined in quality with each successive issue, and usage never became widespread with barter of goods remaining the major medium of exchange.

After the final of the 12 coins, the Kengen Taiho, was minted in 958 A.D. Japan shut down its mint after two and a half centuries of operation. Following this no coins were minted for 600 years. Coins were imported during this period right up until the Meiji era (1868 – 1912).

With no Japanese coins minted from 958 through to 1587, at the same time the economy was rapidly expanding, the burden fell to imported coins from China, Korea and Annam (now part of North Vietnam) to fill the gap.

Gold dust was exchanged, and initially transported in bags and bamboo. Eventually this was replaced by ingots, which were often cast in bamboo patterns. Value was determined by weight and thus there were no descriptions of denomination on the coins. The most common coin in circulation was the Eiraku Tsuho which was imported from China.

During this period the imported coins sometimes fell short of needs, and private mints were set up which copied earlier minted and imported coins. For example, Bitasen, the pre-18th century coins of Japan were neither made under imperial auspices or under the authority of the Tokugawa clan. Shimasen were also copies of earlier coins. This led to a mix of coinage in the marketplace, and people demanded a discount for Bitasen – this practice of selecting coins was known as erizeni.

It was in the Tokugawa Period (1603 to 1868) that Japanese coins started to have standardized values with inscriptions and a gold standard was introduced. The ryo became the unit of currency, with four bu equal to one ryo and four sho equal to one bu. The mon coin was the smallest unit, with 4,000 mon making up one ryo. Initially the mon was minted in bronze, copper and iron and all the other denominations in gold. Later on the bu and shu were minted in silver.

Gold oban were 10 ryo in value, gold koban were one ryo in value – these were both produced as gold slabs. The bu and shu were produced in rectangular pieces of gold.

The Tokugawa currency was not a great success, and in fact was debased ten times. In the end Mexican 8 Reales were introduced with a counterstamped Japanese character to make it legal tender. With the arrival of Commodore Perry, who compelled the opening of Japan to the West with the Convention of Kanagawa in 1854, the need for modern coinage became clearer than ever

The reign of the Tokugawa shoganate came to an end in 1868 when the emperor was restored and the Meiji era commenced. As part of the many changes that were introduced in the Meiji era a modern mint was built in Osaka using machinery imported from Hong Kong. Initially the government expanded the supply of Tokugawa-style coins and produced new one bu, a gold two bu, and a two shu. With the New Coinage Act of 1871 the yen was established as the standard unit of currency, and Japan embarked on an era of modern coinage.