I agree with Jerrys post above but I thought I'd add the following. The quality of these rifles is unparalled and I hate to think what one would cost if it were made today.
If this were mine I'd probably get the unecessary holes welded and just keep the ones for the mount of my choice. The ones on the side of the receiver may in fact be original as many 22s were drilled in this manner for the old Weaver "N" mount. This was sort of the standard mount before they began milling a standard dovetail slot in the top.
Jim
