Took another look at that Model 1 1/2 today, put some money down on it and took a couple of pics.
F75gunslinger,
With serial number 3964 it should have the special mainspring adjusting cam screw (eccentric strain screw) located inside the grip frame under the grips. This was used in the first 6500 manufactured (although I have my grandpa's with serial number 7692 that has the same eccentric strain screw). The remainder of the 97,500 manufactured, had the strain screw on the outside of the grip frame.
The grips shown in your photos appear to be the correct ones for this serial number. There were three styles of hard rubber grips:
Serial numbers 1-15000 were plain checkered with no S&W logo. Also plain wood grips.
SN 15000-29000 were checkered with plain block letter S&W logo.
SN 29000-97500 were checkered with fancy intertwined S&W logo.
Attached is a photo of the early & late stain screw location & my grandpa's with a factory letter that was written in 2014.
Dave