This is a ken shaped tantô from the Yamato Senjuin school. This schools the oldest of the five main schools that comprise the Yamato tradition. It flourished from the Heian era to the Nanbokucho era. This ken has been attributed to the chu-Senjuin school of the late Kamakura era to the early nanbokuchô era of the early to mid 1300’s making this sword about 700 years old. For more information about this school, I would like to refer you to the following article Yamato Senjuin.
This ken measures just a hair under nine inches in length. It has a moto-haba of 0.70 inches or 1.78 inches and a saki-haha of 0.61 inches or 1.55 cm. The jigane is well forged in a flowing masame hada with traces of mokume hada. The hamon is a very shallow notare-midare done in nie deki.
The nakago shows great age and is unsigned. It was awarded NBTHK Tokubetsu Hozon papers in 2002 that attest to the attribution, quality, and condition of this beautiful tantô. It comes in a shirasaya with a sayagaki by Michihiro Tanobe confirming the quality and the fact that it is from the early Nanbokucho era. It is in perfect polish with no defects or flaws of any kind.