So it started off as I as buying scope mount filler holes for my 39a and 39m. The 39m ones went right in. I moved onto the 39a, can't get them in. Then I started thinking, I wonder if these holes are original. The 39m is a '78 and the 39a is a '52. What year if any did the 39a's come out with scope mount holes.

A 52 gun wouldn't have been drilled. They didn't start drilling them until around 58 or so. Looks like whoever did yours drilled it for #6 screws, factory is 8x40.