Hoard of 100,000 centuries-old coins discovered in Japan

Archaeologists in Japan have unearthed a massive stash of about 100,000 coins in Maebashi, a city about 60 miles (100 kilometers) northwest of Tokyo.

The hoard was found during excavations ahead of the construction of a factory, reported The Asahi Shimbun, a newspaper in Japan. Only 334 of the coins have been examined so far, with the oldest one originating from China and dating to 175 B.C. and the most recent coin dating to A.D. 1265, the newspaper reported.

The coins were found in 1,060 bundles, with each bundle containing about 100 coins, The Asahi Shimbun said. The oldest coin has the Chinese inscription "Banliang" engraved on it. Banliang coins were commonly made in China around 2,200 years ago; the inscription translates to "half ounce," according to the Metropolitan Museum of Art in New York City.

A number of coin hoards, including examples bigger than this one, have been found throughout Japan, Ethan Segal, an associate professor of history at Michigan State University who was not involved with the find, told Live Science in an email. "Caches of buried coins, mostly from Japan's medieval period — 13th through 16th centuries — have been found in many locations around the archipelago," he said.

It wasn't until the late seventh century that "the Japanese first started producing their own metal currency," modeling the pieces after Chinese coins with square holes in the middle, Segal said. "The hole was used so that people could string together large amounts of coins, generally 100 coins per string," Segal added. From online pictures of the hoard, it appears that many of the coins have square holes.

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"The Japanese made their own coins until the mid-10th century but stopped at that time due to changes in the economy and an inadequate supply of copper ore," Segal said, with Chinese coins sometimes being used instead. Segal said he would not be surprised if many of the coins ended up being from the Northern Song dynasty (960 to 1127). The Northern Song manufactured large amounts of coins, but after they were overrun by a nomadic group called the Jurchen in the early 12th century, their coins lost value and people were more willing to use them to purchase goods abroad, Segal said.

Why bury a hoard?

A number of large coin hoards have been found in Japan, but why they were deposited is a subject of debate among scholars.

"The hoards may have functioned as a bank. Another theory is that hoarding had a symbolic meaning, possibly religious," William Farris, a professor emeritus of Japanese history at the University of Hawaii at Mānoa who wasn't involved with the find, told Live Science in an email. "I favor the theory that the coins were a type of bank for safe-keeping."

Another idea is that the Japanese buried them in times of war. "They are heavy and bulky to take with you if you have to flee hostile forces," Segal said. However, some scholars "have proposed that coins were buried as offerings to the gods," Segal said, noting that "there is no scholarly consensus."

Who buried them, and when?

Scholars may be able to determine when the hoard was buried, and perhaps who buried them. The latest coin dates to 1265, suggesting that the hoard may have been deposited not long after, Farris said. This dates to the Kamakura period, a time when warriors of Japan took on a greater role, establishing a shogunate (a system in which the emperor effectively allowed a shogun, or military governor, to rule) based at Kamakura, near modern-day Tokyo, according to the Metropolitan Museum of Art. The hoard's location and time period "suggest that the depositors were warriors in the region," Farris said.

However, dating the hoard may be premature at this point, as only a small number have been examined and it may contain coins that date to later than 1265, Segal said.

"It's more common for large coin caches like the one at Maebashi to date to the fourteenth century, when warfare was more common as the Kamakura collapsed," Segal said.

Some of the coins are on exhibit in the lobby of the Maebashi cultural protection division, a statement from the city said. Archaeologists involved with the excavation did not comment by the time of publication.