The problem is not that S&W has/had a model numbering system, it is that they have had many. They started with a fairly simple two-digit system (Model 10, Model 19, etc.). Then they decided to adopt a system that would incorporate other information. And things went down hill from there. Worse, they no sooner got everyone up on one system, than they went to another.
Then us old timers still call the guns by their old names, like M&P or Combat Magnum or K-22. Not to mention the famous "Victory Model", which was an advertising term, was never put on a gun, and was never used by the military.
Jim