This robust tanto from the forge of Yasuchika is a late Edo period Shinshinto work. Yasuchika was the son of Hidechika and both were teppo kaji (matchlock gun makers) so their knowledge of making strong steel was paramount. It was not unheard of for gun and armor makers to cross over into sword smithing to supplement their income as there was limited demand for armor and guns.
Yoroidoshi are thick in kasane, and quite heavy in hand as they are intended for piercing armor lams or chain mail. They also have a sori called "uchizori". Instead of curving upward through the length of the sword, these have a little reverse sori that drops the point toward the linear center of the blade. This promotes the translation of force from the hand through the center of the length of the blade during the action of stabbing and therefore less upward deflection again harder targets as a normal sori or even a sword with no curvature would have. The thick cross section and full niku also reinforce the structure of the sword for durability and increased mass that add to piercing force.
The forging in this tanto is impressive and the shape intimidating. The large itame hada has areas of mokume, and is filled throughout the length with dense black swirls of chikei and jinie as a Shoshu sword should. These chikei are regarded as an indication of a swords qualitative composition and material strength. The hamon is komidare based on suguha in ko-nie deki. Fine ashi and yo are inserted in the yakiba, and the habuchi is strewn with kinsuji, inazuma, and even a little sunagashi. Whirls of activity are contained in the komaru boshi, and kinsuji stream back into the ji from it. This sword is an obvious nod to Etchu Norishige's work style.
Nagasa: 25.8 cm
Motohaba: 2.5 cm
Kasane: 8.8 mm
It is in good polish, has a solid silver habaki, a nice shirasaya, and three papers all documenting the authenticity and quality of the piece;