With regard to finishes, generally, any model number that begins with a "6" is stainless steel or silver-anodized/clear-coated aluminum alloy. Any model number that begins with a "0", "3", "4", or "5" is blued steel or black-anodized/clear-coated aluminum alloy (or scandium alloy). There are exceptions, of course.
With regard to features or caliber...no there isn't really any scheme.
A listing of calibers/models (mostly complete):
.22 Long Rifle caliber: Model 34, 35, 43, 63, 317
.22 Magnum caliber: Model 51, 351, 650, 651
.32 Long caliber: Model 30, 31
.32 H&R Magnum caliber: Model 032, 331, 332, 431, 432, 631, 632
.327 Federal Magnum caliber: Model 632
.38 S&W caliber: Model 32, 33
.38 Special caliber: Model 36, 37, 38, 40, 42, 49, 50, 60, 042, 337, 342, 442, 460 (perf. center), 637, 638, 640, 642, 649
.357 Magnum caliber: Model 60, 340, 360, 640, 649
9x19mm/9mm Luger caliber: Model 940
Hammer Configuration:
Most of the differences have to do with exposed vs. shrouded vs. concealed hammers and the materials the frames (and sometimes cylinders) are made from.
Exposed hammer spur/"Chief's Special":
Models 30, 31, 32, 33, 34, 35, 36, 37, 43, 50, 51, 60, 63, 317, 331, 337, 351, 360, 431, 631, 637, 650, 651
Shrouded hammer spur/"Bodyguard" (anti-snag, but can still be cocked for single-action firing):
Models 38, 49, 638, 649
Concealed hammer/"Centennial" (double-action only, internal hammer):
Models 40, 42, 032, 042, 332, 340, 342, 432, 442, 460, 632, 640, 642, 940
Frame/Cylinder Material:
Most 2-digit model numbers are carbon steel-framed, and most 3-digit model numbers are stainless steel or alloy framed (some exceptions, of course).
Carbon Steel frame (blued or nickel-plated):
Models 30, 31, 32, 33, 34, 35, 36, 40, 49, 50, 51
Stainless Steel frame:
Models 60, 63, 640, 649, 650, 651, 940
Aluminum Alloy frame w/ steel cylinder/"Airweight" (black anodized, nickel plated, or silver anodized):
Models 37, 38, 42, 43, 032, 042, 431, 432, 442, 460, 631, 632, 637, 638, 642
Aluminum Alloy frame w/ Scandium or Titanium cylinder/"Airlite"
Models 317, 331, 332, 337, 340, 342, 351, 360
(the 317 is a bit of an exception, with its frame, cylinder, and barrel shroud all made from aluminum alloy)
Model Number Lineage:
In many cases, the modern model number (3xx, 4xx, 6xx) is based on the historical model number, for example:
S&W Model 42 (black alloy "Centennial" frame, grip-safety, blued steel cylinder, concealed hammer, .38 Special)
S&W Model 042 (black alloy "Centennial" frame, no grip-safety, blued steel cylinder, concealed hammer, .38 Special)
S&W Model 342 (black alloy "Centennial" frame, no grip-safety, scandium cylinder, concealed hammer, .38 Special)
S&W Model 442 (black alloy "Centennial" frame, no grip-safety, blued steel cylinder, concealed hammer, .38 Special)
S&W Model 642 (silver alloy "Centennial" frame, no grip-safety, stainless steel cylinder, concealed hammer, .38 Special)
Same for the 37 (37, 337, 637) and 40 (40, 340, 640, 940).
Sometimes, the lineage goes from the blued to stainless to alloy models, as in the .38 Chief's Special:
S&W Model 36 -> S&W Model 60 -> S&W Model 360
And to further confuse things, some models were built both as .38 Special-only and .357 Magnum versions, usually with concurrent dash-numbers. For example, the Model 60: S&W Model 60 no-dash through -8 are .38 Special only. S&W Model 60-9, -10, -14, -15, and -18 are .357 Magnum, while S&W Model 60-11, -13, -16, and -17 are .38 Special.
Back when model numbers were first stamped on S&W revolvers (1957), Models 10-19 were K-frame guns, 20-29 were N-frame guns, and 30-38 were J-frame guns. Things changed with the Model 39 (9mm semi-automatic pistol, single-stack, double-action/single-action, slide-mounted safety), and model numbers were assigned as guns were developed:
40 (J-frame revolver, .38 Special)
41 (semi-auto pistol, .22LR)
42 (J-frame revolver, .38 Special)
43 (J-frame revolver, .22LR)
44 (semi-auto pistol, 9mm)
45 (K-frame revolver, .22LR)
46 (semi-auto pistol, .22LR)
47 (semi-auto pistol, 9mm)
48 (K-frame revolver, .22 Magnum)
49 (J-frame revolver, .38 Special)
50 (J-frame revolver, .38 Special)
51 (J-frame revolver, .22 Magnum)
52 (semi-auto pistol, .38 Special)
...you get the idea.
Then the Second Generation semi-auto pistols came along (4xx, 5xx, 6xx) along with the L-frame revolvers (2xx, 5xx, 6xx), stainless N-frame revolvers (6xx), and then the 3rd Gen semi-auto pistols (4xx, 9xx, 1xxx, 3xxx, 4xxx, 5xxx, 6xxx)...and then this explosion of J-frame revolvers (3xx, 4xx, 6xx). As you can tell, it's pretty confusing with the model numbers all running together.