Nobutsugu, catalogued with the group of , is known through a single signed with a blade length of two three two , recognised as a on 20 December 1934. The name was used by more than one smith, and the published sources place this blade within that series: 「延次は銘鑑では鎌倉時代初期より同銘数工存在するが、この作は、鎌倉時代中期、文永頃と伝えられるものに該当するであろう」 (according to the registers several smiths of this name existed from the early period, but this work probably corresponds to the one traditionally placed in the mid- period, around Bun'ei, 1264 to 1274).
The is described as 「細身小切先のよい姿である」 (a fine form, slender with a small ). Its 「鍛え小板目約み、地沸細かにつき、映りごころがある」 (forging is a tight with fine and a suggestion of ), and the temper is recorded as 「刃文匂出来多少小沸づいた直刃に小足入る」 (a somewhat touched with , with entering).
The was owned at recognition by Konoe Fumimaro in Tokyo and is now in the Yōmei Bunko in Kyoto. It is published in the Kōzan , the Imamura , both editions of the Nihontō Kōza, Nihontō Zuikan and Ōshirōto no. 18. This single blade is the whole of his present record, and it fixes this Nobutsugu in the Bun'ei years of the mid- period.