Poyer & Riesch says 'early' Type 3 M1 Garand apertures had rounded ramp shoulders and 'later' Type 3 apertures had squared shoulders. Is there any consensus as to approximately when (date or serial #) SA apertures were changed from round to square shoulders. My Springfield M1 is in 784,xxx range (8-42) and I would like to find a period correct aperture if possible. Thanks for your help.
