Antique Scabbard Or Handle Part Japanese Samurai Sword

This is a strange part, not sure exactly what it is, it came on a scabbard or a sword, but it did not belong there. Someone put it on a while back. I think this may be something that goes on a handle maybe in place of menuki, i guess it could belong on a scabbard (but not t he one it came off). There is writing on both sides. The patina is decent and paint seems ok.

If you know what this is, or need it to finish your sword great! Or maybe it would be good to have as a spare, parts are getting hard to come by. My guess is this dates from the 1800's. Theis is genuine, not modern reproductions.