What Jim K. said
The screws are the first thing I look at on a used revolver.
Even a good Smith using the correct size hollow-ground bits will leave some marks on the screws. This gives me pause.
If the screws are buggered up that indicates sloppy work/incorrect tools just to open it so what did he do to the insides ???, and unless the gun is cheap/hard to find and in otherwise very good condition I will pass on it.