Yes, Alf... that is the area I was talking about.
I have enlarged and enhanced your photo, and IMHO, the uneven bottom of the cut on the flange (Arrow A), combined with the fact that the surface of the serations are in the white and not blued, and the small scratch at the top (Arrow B) of the flange, leads me to believe that this was a post manufacture repair or modification to correct some damage to the exposed corner of the flange. Possibly the pistol was dropped on a hard (concrete?) surface which raised a burr that might have interfered with proper operation of the sear/sear spring. Unfortuately, the file that was used was the wrong type and it left the serations which are very similar, but larger than the serations on the rear surface of the front sight. A proper file would have left a relatively smooth surface, but would still be white, and not blue.