Oberndorf seldom ,if ever,mounted scopes themselves.They were usually were mounted by a local gunsmith. If the dovetail pierced the reciever ring, the proof house was susposed to turn it down.You sometimes see a base soldered to the reciever ring with the dovetail cut partially into it and partially into the reciever ring. The reason for the double square bridge Mauser was to allow the dovetail to be safely cut.
Mike