The article is calling it one of "Japan's oldest Nihontō", dating from the end of the 12th century. It was found 80 years ago among some other swords hidden in the rafters of a treasurehouse on the grounds of Nara's Kasuga Taisha shrine. It was recently polished by Hon'ami Kōshū as one of the events of the shrine's ritual rebuilding (once every 30 years). After polishing, the sword was declared to be a Kohōki (古伯耆) sword made by Yasutsuna. It is accompanied by black lacquer saya dating from the middle ages, and it is thought the sword was presented to the shrine sometime during the Nanboku - Muromachi period.
On display at Kasuga Taisha until March 26th.