Period: Tensho (July 1573-December 1592).
Mei: Bizen (no) Kuni Osafune Sukesada. On the reverse, Tensho 6 nen 2 Gatsubi (February 1578).
Sugata: Shinogi-zukuri, tori-zori, iori-mune.
Overall length: 36.85 inches (936.00 mm)
Nagasa: 28.27 inches (718.00 cm) long.
Nakago: Suriage, 8.58 inches (218.00 mm), kuri-jiri, two mekugi-ana. The yasurime are katte-sagari.
Kissaki: Chu-kissaki, 1.70 inches (43.13 mm). The boshi is ko-maru.
Moto-haba: 1.42 inches (36.00 mm). Moto-gasane: 0.29 inches (7.27 mm). Saki-haba: 1.26 inches (32.10 mm). Saki-gasane: 0.23 inches (5.80 mm).
Sori: 0.45 inches (11.32 mm)
Hamon: Midare with ashi, yo, kinsuji, fine nie/nioi.
Very good polish. Some ware on one side towards monouchi. However, these are allowable in a Koto blade.
In shirasaya. Silver one-piece habaki.
Bizen is the only province that achieved continuous sword production from the Heian period to the Shin-shinto period. The conditions were ideal; "Bizen tetsu" (Bizen iron) was exceptionally pure whilst the wood grown in the area produced the highest grade charcoal. It was also significant that the Sanyodo highway passed directly through Bizen.
The decline of the Ashikaga shogunate had started with Yoshiteru's assassination in 1565AD. Ashikaga Yoshihide briefly assumed the shogunate, but died in 1568 from a contagious illness. Oda Nobunaga then marched his armies into Kyoto and installed Yoshiteru's brother, Yoshiaki, as a puppet shogun. In 1573 Oda Nobunaga ended the Ashikaga shogunate, and started a new era, when he drove Yoshiaki out of Kyoto. Oda Nobunaga marked the occasion by naming the new era 'Tensho' the name being drawn from a poem by the Chinese poet Lao Zi. Yoshiaki subsequently became a Buddhist monk, shaved his head and took the name of Sho-san.
The end of the Ashikaga shogunate unleashed a violent civil which drove the demand for swords to incredible levels, and the unrest did not cease until Tokugawa Ieyasu assumed the shogunate. The Osafune Sukesada smiths were the principle suppliers of swords for these wars. Demand for their swords was so high that many were mass produced. If the mass produced swords were signed at all, it was with the short form, Bishu Osafune Sukesada.
The mei is the long form, indicating that it is much higher quality than the mass-produced blades. In addition, the mass produced swords were not generally dated; in fact few Koto blades are dated. The blade is, at nearly 72cm, unusually long for Muromachi period work, and probably saw service all the way through the wars leading to the unification of Japan under Tokugawa Ieyasu's shogunate in 1603 AD.
In 1590 the Yoshii river catastrophically flooded, wiping out the forges in Osafune. This marked the end of the greatest of the Koto traditions.