Yoroi-doshi style (see the bottom of this page => Yoroi-doshi)
blade length 19.4cm, thickness at the base 7mm, width 19mm
The steel is clear and bright. The surface is full of steel particles (ji-nie) and chikei. It is beautiful.
The hamon also is bright. The hamon exists not only on the cutting edge, but also on the back. That means the edge of the back also hardened. The hamon include much kinsuji and sunagashi.
When you study the hamon and utsuri with proper light, the appearance of steel particles (ji-nie) is not simple. The steel surface is full of ji-nie, but the denseness of them is not flat. The density of particles is uneven in parts. But the border between the dense spots and thin spots is not clear. The fuzzy border makes a misty midare-utsuri, but we can't catch it as a simple pattern. Some yubashiri also appear. So the appearance changes by different angles of view. It is difficult to check up all the faces of steel particles. It seems an endless pleasure to study steel particles. That fantastic appearance comes from the complicated relation between hardening work, steel quality, and the wearing of the blade.
Tang
signature "Tadamitsu"
Tadamitsu is a smith in Osafune school from 14th century to 16th century. There are several generations during that period. This Tadamitsu is in 15th-16th century (around 1500AD).
This is a good quality blade, though it is worn. The polishing is the classical style (Sashikomi style) without any trick. So you can study the blade quality honestly. This blade was made as weapon, so the quality is far better than some art swords in Shinto period. The clearness of this blade is what we appreciate on Japanese blades. We want you to see what good blade is.
Habaki, it shows the cross section of the blade.
YOROI-DOSHI
"Yoroi" means armour, and "doshi" means go through. So yoroi-doshi style is specially purposed blade to go through armour. Usually such blade has large thickness, small width, no curvature or a little down curvature, and short length around 20cm. The hardened area (hamon) is not only on the cutting edge, but also on the back. The hard edges of the back also work to split target. The tang is long to grip the handle firmly. That style is produced to get good work to stick tough target, rather than sharp cut. Some of moroha-zukuri style tanto with large thickness is yoroi-doshi too.