Gerben,
You have pointed out the best clue. In general, all the checkering and grooves on the reproduction sight are finer, i.e. more lines per inch. Also the vertical grooves on the sight "ears" are shorter than the original,the trailing profile of the ears has a longer radius and a shorter vertical slant at the rear, plus the original has a larger radius on the edges of the toggle knobs,etc. These features could probably be reworked by a forger, but some vestige of the finer lines would probably remain, particularly on the linear knurling on the "barrel" of the toggle knobs. This knurling is either done mechanically with a device similar to a roll die or forged, so the metal is "upset" at the ends of the lines (sort of like the condition that creates the "halo" on barrel serial numbers). Hand cutting these lines leaves a smooth transition to the un-knurled area.
