SureFire did use a convention for WeaponLights to identify the handgun each was designed for:
1 = Glock
2 = Springfield XD
3 = SIG P220
4 = SIG P226, P228, P229
5 = H&K USP (Full Sized)
6 = Beretta (92F/SB, 96F)
So the Series identifier came first:
P = Nitrolon
M = Millennium
W = Military
Then came "1"
Then came
"0" for Constant-On Shuttle Switch, no remote switch.
Or
"1" for remote switch.
The third digit was for the handgun model
and if the second digit was as 1, then
"C" for Constant-On Shuttle Switch,
or
"D" for Disable Shuttle Switch.
Some models featured a so-called -DG or Dev Group remote switch rather than the standard 'SlimLine' remote switch.
SureFire carried over the handgun model identification digit to the X200/X300 remote switches noting that the X-Series was designed to fit on rail-equipped handguns.
SL- for SlimLine
DG- for Dev Group
Then;
11 = Glock
12 [not used AFAIK]
13 = SIG 220R
14 = SIG 226R, 228R, 229R
15 = H&K USP Compact
16 Beretta FS92
17 = 1911
18 = 1911 TRP
19 = USP Full Size
20 = Beretta Vertec
I could go on and explain about the MR mounts but I've digressed enough!