Hamon (from Japanese, literally "blade pattern") is a visual effect created on the blade by the hardening process. The hamon is the outline of the hardened zone (yakiba) which contains the cutting edge (ha). Blades made in this manner are known as differentially hardened. This difference in hardeness results from clay being applied on the blade prior the cooling process (quenching).
Tachi koshirae are usually not my cup of tea but i wouldn’t mind to own this beauty By the way, a closup of the tsuba has been posted here. Picsource: bonhams.com Samurai Sword Shop Info CenterUSA firstname.lastname@example.org