The earlier guns with two different size screws took a #10-36 and a #5-48. Later they went to two screws the same size with a closer hole spacing that are either #8-40's or #6-48's, I don't remember which. The #10-36 is the same size as used by Winchester for the front tang sight screw, those can be found, the #5-48's are a lot harder - Stevens used a #5-44 for tang sights and #5-40 seems to be available, but not #5-48's. I found a tap & die set for those and thread my own.

The Savage Model's 1904, 1909, 1911 and 1912 also used #5-48's to attach the barrel sight. These are all button head screws, so not much good if that type head will not work.