S&W standardized it's screw sizes:

The sideplate and stock screws specification change order of March 4, 1942 was just that: a specification change in the standardization of tolerances for screw diameter. A change from old S&W 'smaller minimum diameter' tolerance to the larger minimum standardized tolerance of the #5 National Fine (N.F.) screw diameter (no, the 44 threads per inch did not change). It refers specifically to the sideplate screws (but excluding the bug screw or upper sideplate screw which is a 4-48 pre and post war) and also the #5 N.F. stock screws. Therefore, there CAN BE a difference between 'pre-change' and 'post-change' screws and they CAN measure different diameters. Sometimes they are interchangeable and sometimes not. After 3/4/42 K & N stock screws became #5-44 NF with an upper OD tolerance of .125" and usually measure .122”+or-.

Prewar K & N stock screws were 44 TPI but the O.D. upper tolerance was only .122" but usually measure closer to .119"+or-. Therefore, if you try to use a standard 5-44 or a post war stock screw, they are a bit oversize. One or two thousandths isn't a lot but makes a big difference on such a small diameter. Usually 5-44 /post war stock screws can be made to work by decreasing the OD with fine grit sandpaper.
Just FYI, pre war I frame stock screws are close to a 3-48, but again, slightly smaller in OD. I & J frames became a standard 3-48 until I frames were discontinued and ~ 1980s when J became 5-44 also.

The 1988 new larger yoke retention screw with plunger is 8X36 and non-fitted.

__________________
Jim
S&WCA #819