jt, Of considerable importance is whether or not the rifle is a square bridge action. Being a square bridge with the dovetailed front claw mount in the receiver ring would mean it most likely (but not necessarily) was done at the factory (the dovetail). Not being a square bridge would mean it was most likely done by a gunsmith (but not necessarily). There exists factory square bridge rifles with uncut front rings that were never scope mounted. The most common scope mounting on model B's you see is the double claw mount where the front is dovetailed into the ring and the rear is screwed to the bridge. Most of these were not done at the factory (from what I understand) according to Speed's book. Not being done at the factory would mean it would not have been proofed at the Oberndorf proof house and most likely not proofed at all. Mauser was proud of their scope mounting design and promoted it (the square bridge with mortised push button rear mount and dovetailed front claw mount). Speed does state that different scope mounts could be special ordered from the factory. But as stated if scope mounting was desired after the rifle left the factory it usually tends to be the double claw mount done by a gunsmith. See picture above.