Mine is a AG-42b and it is 6.5x55. a B is stamped into the left side of the receiver after the serial number , the dust cover (I guess thats what its called)and the rear sight are also stamped with a B. It does have the rubber buffer. On the right side of the receiver there is S.S. stamped into it. It is dated 1943. If this was an unissued rifle could it be missing the disk, thats what I"m thinking as the stock is like new with the exception of a few small dents next to the trigger on the left side. This rifle is like new. almost no wear, all matching numbers, Blueing 99%,