Bsa bsa murcury Murcury .22

Bsa murcury im told its a mk1 but i dont know how to identify the differences. Got this as a none firer wouldnt cock so ive just removed the sized in piston the buffer washer had disolved so was blocking the piston movement.ive fitted new piston buffer and seal also new breach seal.so now shoots well .ive left the rest of the gun alone will make a nice project for someone please study pics as they form part of the description.