Photo/Illutration A black substance is seen on a stone artifact from the Tawayama ruins. (Provided by the Matsue city government)

A black mark on a stone artifact believed to be the oldest known written character in Japan was likely made with a modern permanent marker.

A research team that included the Archaeological Institute of Kashihara, Nara Prefecture, reached the conclusion after analyzing the 2,000-year-old artifact.

The team said the “character” was probably made through contamination from a marker.

It will announce the finding at the Japan Society for Scientific Studies on Cultural Properties congress on Sept. 10.

The stone artifact, 9 centimeters long and 7.5 cm wide, was found at the Tawayama ruins in Matsue, Shimane Prefecture. It dates back to the latter half of the middle part of the Yayoi Pottery Culture Period (1000 B.C.-A.D. 250).

The artifact was described as a grindstone in a 2005 survey report.

In 2020, however, Takeo Kusumi, a researcher with the Fukuoka city government’s Archaeological Center, theorized that the artifact was used as an inkstone based on the black mark and other factors.

At a conference of archaeologists, Kusumi said the black mark was likely a character written in ink.

Newspapers and TV programs then ran stories about the “oldest letter in the nation.”

The Matsue city government, which owns the stone artifact, took infrared images but could not confirm the mark was ink writing.

The government also failed to find any particles with shapes characteristic of ink via an electron microscope.

Tomoki Okami, a chief researcher of the Archaeological Institute of Kashihara, cooperated with the Nara Institute of Science and Technology and studied the mark.

Okami analyzed the intensity distribution (spectrum) of a special light that was shined on the mark.

The spectrum matched the characteristics of a permanent marker.

“We believe a stain from a permanent marker accidentally adhered to (the artifact),” Okami said.

A Matsue city official had used a permanent marker to write the locations where stone artifacts were excavated on tags during the sorting process.

The city government said it will ask university researchers to conduct a further analysis.

“I can’t help but accept the latest finding because the researchers followed scientific procedures,” Kusumi said. “If a reanalysis and other examinations confirm the mark is a modern substance, I will completely withdraw my point of view.”

(This article was written by Kenji Shimizu and Kunihiko Imai.)