I made up this list of codes a few years ago. If you cross reference it with the parts list on the S&W web site, you can get an idea of what models exist.

10xx 10mm
22xx .22 rimfire
39xx 9mm single stack
40xx .40 caliber
45xx .45 caliber
59xx 9mm double stack full size
69xx 9mm double stack compact

xx0x TDA full size
xx1x TDA compact
xx2x Frame decocker full size
xx3x Frame decocker compact
xx4x DAO full size
xx5x DAO compact
xx6x TDA mid size
xx7x Frame decocker mid size
xx8x DAO mid size
xx9x Non standard combination

xxx3 Alloy frame silver
xxx4 Alloy frame black
xxx5 Steel frame blue
xxx6 Stainless steel frame
xxx7 Non standard combination

There are also some 3rd gen guns that have just 3 numbers. They include the econo-line and some PC .45's.