Late Kamakura period Tachi blade attributed by Sairen.
Late 13th century-early14th century.
The blade is not signed but attributed by Sairen and the blade is in the Shirasaya mount which has the Saya-gaki authenticity in 2012 (or 1952: the Saya-gaki date was written with conbination of two zodiac signs: Ushi-ox & Tatsu-dragon) by well known Tanobe Michihiro.  Mr. Tanobe Michihiro published a number of Japanese sword books.  The Katana smith Sairen is late Kamakura period and this quiet Hamon blade in good condition has the first authenticity paper of Tokubetsu Hozon by N.B.T.H.K. (Nippon Bijutsu Token Hozon Kyokai) of 2013.  Next application paper should be as Jyuyo Token, (the important sword) by N.B.T.H.K.
Note: Mr. Tanobe Michihiro mentions this blade is very much "Ubu" (not shorten and in original state) which is very important.
A couple photos of the blade is available by request.