katana signed NAGAMUNE Nyudo-saku

Shinto early Edo period (Enpo era/1673-) Bushu
Length of cutting edge 75.2cm Curvature 1.5cm Width of Base 29.2mm Width of Yokote 18.5mm Thickness of base 7.9mm

NBTHK(Tokubetsu Hozon) certificate

Blade construction: Heroic long Katana of Mitsu-mune back ridge with ample thickness. Mihaba on base is in average and the Nagasa measures around 75cm holding a well harmonized Sori curvature but the blades tapers in a bit strongly that ends in medium Chu-kissaki. (click HERE for super sized image of entire blade)
Forging(Hada): Kitae is fine Masame-hada straight grain. The entire skin of Hiraji shows sparkling martensite crystals of Ji-nie to generate darkish gleaming lines of Chikei activity.
Temper(Hamon): Hamon of boundary line is Suguha straight with shallow waves with some indications of Hotsure flay and small Gunome. Sparkling Nie piles up on boundary line like a virgin snow with deep martensite crystal of Nie and the interior is filled with mist-like Nioi. The entire Hamon is remarkably glossy with appearance of antiquity.
Temper of tip(Boshi): Hamon of Boshi wide straight with brushing Hakikake indication then medium circle turns back.
Tang(Nakago): UBU in original. Two original Mekugi-ana retaining holes. Katte-sagari slanting left filemarks. Uneven round shape bottom heel of Ha- agari Kurijiri. Back ridge is a bit contoured with greatly slanting left of Ō-sujikai filemark. The Tachi-style upright Buddhist (Nyudo) inscription signature in well-mannered 5 character is engraved on Hiraji-surface NAGAMUNE 長宗 then the name of priest Nyudo-saku 入道作.

The smith NAGAMUNE 長宗 (considered the same artisan who named himself NAGAMUNE 長旨 in different Kanji character) , real name Ogasawara Sakyo 小笠原左京 was raised to the status of Samurai as a son of Ogasawara Toukuro 小笠原藤九郎.
After having worked for a vassal of his master
Abe Iyo-nokami MASAKATSU 阿部伊予守正勝 in certain period, he made up his mind and started going to be a blacksmith of horse bit as well as Yoroi amour and was in the nature to become a swordsmith then set up his alterer at Ikenohata 池之端 in Bushu (present Tokyo).
He followed Yamato tradition like this example and his extant works with date of year ranges from Kanbun to Ten'na (1661-83). He ranks as the "Jou-jo saku" Above Superior Made and awarded as the "Wazamono" for its sharp cutting performance in the list of "Ko-kin Kaji-biko" 『古今鍛冶備考』 issued by the swordsman Yamada Asa'uemon 山田朝右衛門.
His katana received great fame as not only it's cutting performances but also beauty of forging and quenching technique from traditional Yamato tradition to maintain a proud independence in Busho Edo and his extant works are quite rare to be highly treasured in generations.
This katana is designed the most usability first that holds appropriate curvature for the fast draw and rich volume of thickness with high Shinogi-suji is highly concerned about durability from hard hitting. Super brilliant quenching temper is performed for the super cutting performance.
From it's Buddhist priest name of signature Nyudo-saku 入道作, this katana was made in his later years after the 2nd generation became independent.
Gold folied double layer Habaki collar, preserved in Shirasaya plain wood mounting.
Good old polish/Condition scale: excellent (using a scale of mint-excellent-very good-good-fair-poor)
reference data :
Ishii Masakuni/Honma Kunzan, Nihonto Meikan, Yuzankaku, 1975
Fujishiro Yoshio, Nihon Toko-jiten, Fujishiro shoten, 1974