Isn't the 4th screw on the upper portion of the side plate? I think that must be a 3 screw non marked as Model 29. A beautiful gun never the less! I don't think there are many 5 screw .44 magnums as by 1957 they were going to 4 screws. I think 4 screws went away in 1962 or 63, I was just getting into college, and the .44s were pretty exotic!