Most Lyman 48's have horizontal holes for mounting. One underneath the slide, the other on the side of the slide.
However, on some for the Model 52 target, the sight mounts
on the rifle using a large dovetail. Here is a link
to a picture of that kind of Lyman 48

Lyman 48 for Winchester 52 target

You can see that there is no hole by the side of the slide.I can imagine removing the rail with the dovetail. I don't know what the back of this particular model looks like.