Nihon Bijutsu Token Hozon Kyokai, Token bijutsu, vols. 58-59, no. 13,
The Museum of Japanese Sword Fittings, ed., Tokubetsu ten, Edo jidai no katana to tosogu (Special exhibition of swords and sword fittings from the Edo period), exh. cat. (Tokyo: Museum of Japanese Sword Fittings, 1999), no. 9, p. 9.
Okimasa was the pupil and adopted son of Nagasone Kotetsu (see Christie's, London, Important Swords from the Museum of Japanese Sword Fittings, Part I, 10 November, 2004, lot 17), the most celebrated of the Kanbun-era smiths of Edo. The Nagasone were a family of armor makers originally from Omi Province, who moved to Echizen, from whence Kotetsu went to Edo. The work of Okimasa is close to that of his father, with bright close jigane and frequently having a gunome midare hamon like this blade. The boshi particularly follows the characteristic profile resembling the pad of a human thumb found on most of Kotetsu's blades, although many have a degree of hakikake. Like the work of Kotetsu, the blades of Okimasa were designated saijo o-waza mono (blades of greatest cutting efficacy) by the Yamano family of sword-testers.