How do figure out smith and Wesson models?

There are entire books on S&W handguns, so we can't cover everything in a short answer. Prior to WW 2, S&W had names for their various models. They later numbered the models- so that the Military & Police Special became the Model 10. The Chief's Special became the Model 36. When they added stainless steel guns, the first number became a 6, such as the stainless steel Chief's Special, the Model 60. They are now using 3 numbers to identify specific models. S&W also uses a letter to indicate frame sizes. The smallest is currently the J frame (Chief's Special size) the K frame (size of the Model 10) and the larger L,M, and N frames.