The National Treasure at the Chido Museum in Tsuruoka is a signed Nobufusa (信房作), received by Sakai Tadatsugu from Tokugawa Ieyasu for military merit and handed down thereafter in the Sakai family, lords of the Shonai domain. It is one of two designated works now placed under this Nobufusa, a smith of the early school at the turn of the into the period. He is not the Nobufusa who signed with the characters 延房, a separate smith with his own entry. The published sources record two master smiths of the name in , one of and one of , and the tradition they cite gives the two-character signature 信房 to the smith and the three-character Nobufusa to the smith.
The National Treasure was itself first designated as Nobufusa, on the strength of an archaic, elegant temper based on mixed with . Its commentary records that the attribution has since been reopened: 「近年二字銘信房の新資料の発見にともない再検討されており、古来の伝えのように一文字の信房であるとの見方が強い」 (with the recent discovery of new material bearing the two-character signature it is being re-examined, and the view is strong that, as the old tradition holds, it is the Nobufusa). The is slender, with high and and a small . Its is a well-packed thick in , with a faint and here and there. The is a shallow tone mixed with and , with frequent and and strong , the temper widening in the upper half. The is deeply hardened and well covered in , a in style on the and with on the . The is in a shape, and the three characters are cut above the toward the .
The second work is an signed Nobufusa , designated at the 25th session in 1977. The published sources date it no later than the late to early period, note that 「信房は古備前派と古一文字派に同名がある」 (there are smiths of the name Nobufusa in both the and the Ko- groups), and resolve it by the signature: 「本作は古刀銘尽大全にある三字銘の古一文字にほぼ見合うものと鑑せられ」 (this work is judged to correspond closely to the three-character Ko- signature recorded in the Meizukushi Taizen). They single out its form: 「腰反り高く踏張りつき、先にうつむくこころあり、小鋒という太刀姿が美しく古調である」 (with high and , a slight downward tendency toward the tip and a , its shape is beautiful and archaic). Its differs from the National Treasure's, an with , mixed with and standing out, with a ; is present and some -are is noticeable. The is based on and mixed with , with and entering well, the richly covered in with frequent and . The undulates gently and turns back in , and a is cut on the above the signature.
Both works are therefore three-character , and both are placed with the smith by the same reasoning, the tradition that assigns the sanjimei to . The two designated works on record divide plainly. The National Treasure at the Chido Museum is preserved as patrimony and will not trade; the is the only one of his works in a tier that can change hands, and a blade of this name and period reaches the market only rarely.