What you have is a British Pattern 1853 bayonet that was sold out of service (surplussed), then modified by one of the Liege firms for use on the 11 mm. Mauser M1871 rifle. These were used by Uruguay and Japan. The modified socket is very short (2 1/8 in.) vs. the P1853 socket. The bridge is really thin and the new locking ring has no screw. Compare yours against the one pictured on my site.