As someone also mentioned, there are the .38/44's that can really confuse the new S&W collector. I own S 69847 (8/46) and S 67706 (8/46) an OD and a HD. These really confused the heck out of me when I was trying to understand the M&P's with numbers like S 955509 from 1947 and then 38/44's with numbers like S 69847 and S 67706 shipped a year later.
I have been doing this for 45 years and I still learn every day. Imagine what it must be like just starting out trying to understand S&W's with all of the little nuances with serial numbers and shipping dates.