Hello, I have an original engraved Ballard,   All screws in action & stock fittings are unmarred and fine.  The problem is the two tang sight screws..They aren't real bad..just slight burring around top edge of slots..not all tore up like some.  The patina on screw heads matches perfect with surrounding metal.  Now I can straighten these out no problem..I have done this many times before..the question is..should I?  I doubt I'll ever match that patina, as they look to be untouched forever.  Should I leave them alone?  Thanks guys!

Those tiny little 8-40 screws are commonly replaced, as tang sights went on and off old Ballards. Replacing them wont affect the value at all, as most people expect them to either be missing, buggered or new. Of the 3 I always choose new. 
Most of my old Marlins and Ballards have either new or like new plug screws. I doubt anyone knows which they are. Ballard receivers were casehardened so the screws don't have to match the existing receiver patina anyway. You can hit the heads with 600 grit to take some of the newness off, if it really bugs you.