Iron Sword Excavated in Kumamoto Inlaid with Characters Possibly Meaning Year 604

The Yomiuri Shimbun

17:13 JST, January 28, 2023

KUMAMOTO — Characters that may indicate the year 604 have been discovered on an iron sword that was excavated in April last year from a burial mound in Kumamoto City, the city government announced Friday.

Previously, an iron sword inscribed with characters believed to represent the year 608 was excavated in Hyogo Prefecture, raising the possibility that standardized swords were distributed to various regions during the reign of Prince Shotoku.

The about 55-centimeter-long iron sword was unearthed from the remains of a tomb from the Kofun period at the site of Kumamoto Castle during an excavation by the city government.

The sword’s surface is covered with rust and remnants of a wooden scabbard, but an X-ray CT scan conducted by Kumamoto University was able to confirm the presence of the characters “Koshi” inlaid with metal on the sword. The type of metal has yet to be determined.

Koshi is one of the 60 terms used in the sexagenary cycle. Judging from the sword’s form, which has characteristics of the late sixth to the first half of the seventh century, it is calculated that the Koshi inlaid on the sword likely means 604.

Kumamoto’s discovery is the eighth example of a Kofun period sword with an inscription excavated in Japan.

It is also one of four swords with characters referring to a sexagenary cycle term. These also include the iron sword unearthed in Yabu, Hyogo Prefecture, in 1983, which has the characters “Boshin” inscribed in the same style as the Kumamoto artifact. Boshin is believed to mean 608.

Another such sword is an iron one discovered in the Inariyama burial mound in Saitama Prefecture and designated as a national treasure.

According to Haruyuki Tono, professor emeritus of Japanese ancient history at Nara University, the dates indicate the year when the swords were made. He also pointed out the similarity seen in the inscriptions of the two iron swords.

“The fact that the iron swords with similar inscriptions have been excavated suggests that the same type of sword may have been circulated to small and medium-sized powerful clans in various regions at that time,” said Tono.