Gassan Sadayoshi (1800--1870) was a smith of Dewa province, the home of the ancient Gassan school of sword-making which had been associated with the Shugendo mountain sect since the Heian period. He became a pupil of the revivalist smith Suishinshi Masahide in Edo, and later visited many provinces to study different traditions. The present Gassan family of Osaka descend from his adopted son, Sadakazu. Sadayoshi was proficient in a number of styles, including those of Yamato Hosho and Bizen like the present sword, and he revived the ayasugi hada of the ancient Gassan school. Indeed the jigane of this sword is close to ayasugi hada. Although unsigned, the firm yet sparsely placed osujigai file marks are unmistakable identification of both early and later work of the smith.