Before they used grooved receivers the Weaver mounts you mentioned were the only ones that I know were used, guns set up for them would have two widely spaced holes on the left side of the receiver, I have never seen a factory drilled gun with four holes. Some versions for Montgomery Wards were drilled & tapped for Mossberg scope mounts which used a shorter hole spacing.
You do not mention where the two hole on your gun are located, I assume they are at the rear of the receiver - those would be for a WFC 150 peep sight.
I have a picture showing a gun drilled & tapped for the Mossberg mount and milled & tapped for the No 105 peep sight which is earlier than the WFC No 150. It's an early Savage Model 3 single shot action -
Here are a couple with the Weaver mounts, the top has a four hole mount with two of the holes quite obviously added (that side is not shown) -
Here are a couple pictures of the WFC 150 sight -
Bookmarks