The school of Munetsugu
According to the Japanese Wikipedia, Koyama Munetsugu (固山宗次) was born in 1803 in Shirakawa, in Mutsu province, passed through Kuwana and worked in Edo; he excelled in Bizen-den, and on his blades the edge never carries coarse nie (荒沸, ara-nie). The same article names among his pupils Tairyūsai Sōkan and Tomono Yoshikuni (友野義国).
The signature in reisho
According to Sesko, Sōkan switched to signing in chancery script (隷書体, reishotai) in 1857 (Ansei 4); before that he signed in regular script (楷書, kaisho). Sesko supposes, and says it is without proof, that he learned calligraphy from Ichikawa Beian (市河米庵), who lived from 1779 to 1858, and that the character 寛 (kan) of his name came from Beian’s father, Kansai (寛斎).
The workshop
According to Sesko, he passed the habit of signing in reisho on to his son Tairyūshi Hirotsugu (泰龍子寛次), an engraver, whose name appears in one of his signatures, and to his pupil Issensai Hiroshige (一専斎寛重). In the sources consulted no second swordsmith signing Sōkan is recorded.
What is not on record
His year of birth, his death, his place of origin, the date he joined Munetsugu and his service to a lord are not recorded in any of the sources consulted, and so they are not given here.