Grizz,
This is not meant as criticism, but as a statement of fact: if you are at all serious about S&W revolvers, you need to start with the 3d Edition, Standard Catalogue of Smith & Wesson. It isn't expensive, but it is authoritative.
Believe me, that is one of the best ways to start to understand what you are talking about and looking at -- and the tables of known serial numbers for every model S&W are a gold mine.
Nothing beats knowledge about what you are looking at. That is how a fatally mis-marked and under-priced transition-era Heavy Duty found its way into my accumulation. A hole-in-the-wall dealer who specializes in semi autos thought it was a Model 10 (yeah, the guy, a dealer, didn't even know the difference between a K-frame and an N-frame, apparently.)
Again, this is not a criticism, but a strong suggestion.
Bill