Gents, interesting post. I also have a similiar revolver. The only serial is on the butt. All appears to be a stone cold factory original 29 no dash 4 screw. Any insights?
I think I recall that about the time model numbers were introduced the secondary parts numbering began to disappear. Thus there is a transitional period around 1958 where you might or might not find a serial number on the cylinder, barrel, yoke, and so forth.
There was actually a short period for pre models just before model # stamping and a longer period for early numbered models when the serial # was not in the yoke and only on the butt, backside of extractor star and backside of right grip.