Craig,
The screws are, indeed, one off, and the screw drivers are also. The screw originally had a very thick head, with a sacrificial slot. When every thing was fit up and turned in properly, a new slot location was marked( north and south) and either filed or sawn( with a fine blade),then the head was filed flush, polished and engraved. The screw driver would have been made to fit that screw( and others in that location in other guns made at the same workbench). When the finished screw in under or over turned, then not only is the slot noticeable, but the engraving is mismatched.
With regard to scope rings, the only logical type screw to use is either Allen or Torx.
Mike