Thanks Mauser22, looks like I came pretty close all way down to the 42 TPI, just off on the angle being 55 degree instead of 60 as I measured. As I said, it was one of my better screws but still a used one with probably some wear that kept me from finding the true edge for the angle measurement. Thank you for making the original blueprints available.
Also, 6.35mm diameter for the trigger guard screw per the blueprint makes it exactly a 1/4" 22 TPI screw. I stand corrected regarding my remark "Germans never used odd diameters". They obviously did, even their drawing refers to British Whitworth threads.