CT imaging sheds light on origin of ancient 7-pronged sword

by KUNIHIKO IMAI
May 21, 2025

The Seven-Pronged Sword, a national treasure, is currently on display at the Nara National Museum. (Takayo Oyama photo

NARA—The Seven-Pronged Sword, a treasured fourth-century artifact, underwent a groundbreaking scientific examination using an X-ray CT scan for the first time.

The scan revealed remarkably clearer images of its gold inlay inscriptions, which are expected to advance scholarly understanding of ancient Japanese history.

The sword, which is named Shichishito, is a designated national treasure housed at Isonokamijinja shrine in Nara Prefecture. It features an unusual structure with three branch-like blades on each side.

It bears a 62-character inscription, describing its creation as a diplomatic gift from the royal court of Baekje, a kingdom on the Korean Peninsula, to a Japanese ruler.

The scan was conducted by the Nara National Museum to assess the sword’s condition after more than 1,600 years—described by curators as a “health checkup.”

The imaging revealed a clearer rendering of the character for “je” in “Baekje,” which had previously been obscured by corrosion and debated among researchers.

Another significant finding involves the inscription’s reference to the sword’s creation year.

While most scholars have interpreted it as the fourth year of the Chinese era “Taihe” (369 CE), some have proposed an alternative reading as “Taishi” (468 CE) due to the last character in the word being obscured.

The new CT imagery revealed a clearer shape of the character, strengthening the case for the “Taihe” (369 CE) interpretation.

The study didn’t detect any serious deterioration or cracks, according to Satoru Yoshizawa, a senior curator at the museum.

“We didn’t discover new characters, but the crisp images of the known inscriptions are a valuable asset for future research,” he said.

The Seven-Pronged Sword is currently on display at the museum’s special exhibition “Oh! KOKUHO: Resplendent Treasures of Devotion and Heritage,” co-hosted by The Asahi Shimbun and other partners.

The exhibition runs through June 15.

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