This is a really nice 20th Century COPY of a Samurai era Kojiri. Silver patinated to resemble dark Shakudo, of seamless construction, in the form of a Shrimp (although this design is almost universally described in the sword world as a lobster).

Replacement Kojiri are usually only suitable when making a new Saya - the chances this will fit correctly onto an existing Saya without modifications are very slim.