Previous answer is
Mumei(unsigned) attributed as Sekisyu Naotsuna
Special feature: It is generally believed that Sadatsuna
the First was a son of Sekisyu Naotsuna.
Naotsuna has been counted among Masamune-juttetsu,
the best brilliant ten pupils of Masamune in Soshu.
Sekishu province, present Shimane pref. had been prospered
by exporting iron. Using good quality iron,
the clan forged excellent swords for generations.
Appraisal Quiz #590 ( May 23rd, 2020)
Who made this sword do you think ?
Blade length : 71.21 cm or 28.04 inches.
Sori : 2.51 cm or 0.99 inches.
Mekugi : 3
Width at the hamachi : 3.05 cm or 1.20 inches.
Width at the Kissaki : 1.97 cm or 0.78 inches.
Kasane : 0.63 cm or 0.25 inches.
The weight of the sword : 705 grams.
Shape : Tachi with ubunakago. The blade is wide
and thick with deep Koshi-sori and long kissaki.
Jigane : Itame hada and Mokume hada with fine jinie attach.
There are detailed chikei and jihad-utsuri.
Hamon : Basically suguha, little choji and notere are mixed
with ashi and yo. There are many nie, kinsuji and sunagashi in the blade,
and little yubashiri in yakigashira.
Bo-shi is finely disturbed and turns back hakikake style.
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