The serial # you gave should be a model 96.  Four equally spaced holes could be for an old Williams Mount.  I just sold one!  Initially Williams used the same mount that fits on the Remington 8 and 81.  They later changed to one with three holes for the Krag.  They no longer make their side mounts!  Two and two grouped together could be for a Weaver mount as you said.  Put a scope on it if you can find the right mount.  Good for accuracy testing of loads, and if you're getting up there like most of us here, it helps to be able to see what you're shooting at!  With the scope, you'll have a way to shoot it while you contemplate what to do about the sight.