責金 Sekigane / Gilt Metal
What is Sekigane in Japanese Katana terminology?
This is a small metal fitting made of soft metals such as pure copper or silver, applied to the contact points between the handguard (Tsuba) and the blade, and the Tsuba and the ridge, to firmly fix the Tsuba and the blade without any gaps. Some are attached at the time of Tsuba production, but generally, they are added during the adjustment with the blade. In the late Edo period, some were equipped to enhance the decorative nature of the Tsuba.