This is from Marlin Owners. I could spend half the day amending it but this will give you the jist. Just for grins Ill add a few hasty additions and notes in (parentheses)
These are specifically for 336 rifles. 1895s, 1894s, and 444s will have a few others I will detail below.
CS .... Carbine Safety
C........ Carbine. 1968 and up
RC......Regular Carbine same as C prior to 1968
T .......Texan. Carbine with straight stock, 20 inch barrel (quite uncommon and from pre-1970. Not all 336s dubbed "Texan" will have a T designation)
TS.......Texan Safety with 18.5 inch barrel.
SC.......Sporting Carbine, 20 inch barrel, 2/3 mag tube, pistol grip.
CB.......Cowboy, 24 inch octagon barrel and straight stock.
A.........Prior to 1980 24 inch round barrel PG stock
A........ Most recent, 20 inch PG carbine with birch wood, end cap forend.
W........ 20 inch PG carbine, birch wood, and two barrel bands (I always joke the "W" is for WalMart as these were plentiful economy options mostly sold at WalMart type retailers)
Y......... Spikehorn youth model short PG walnut stock 16.5 inch barrel.
LTS...... Texan Safety, 16.25 inch barrel. (Special run)
Marauder.. same as 336 T except has 16.25" barrel and SG. Roll marked RC. (Pre-1970)
ER......... Extra Range PG stock in 356 Winchester. (2/3 mag tube only made a few years in the 80s)
375....... PG stock 20 inch barrel in 375 Win. (2/3 mag tube. May have been made concurrently with the 336ER but was, once again only produced for a few years in the 80s)
XLR.......Stainless steel 24 inch barrel PG laminated stock (Just a guess but ??Extra Long Range?? Maybe since it was developed in conjunction with Hornady Leverevolution ammo)
CC....... 20 inch carbine with camo pattern birch PG stock (Carbine Camo)
SS........20 inch PG stock Stainless steel. (This can also mean Safety Stainless)
ZG....... Zane Grey Century PG stock, 22 inch octagon barrel.
336 Octagon.. 22 inch octagon barrel SG stock.
D - Davidsons Exclusive- Specifically 336D. A 336 in 35 Remington that is in ported guide gun format. Only 1001 made.
336BL.... big loop lever and laminated PG stock.
P - Ported - Marlin released a bunch of P models in the late 90s They are pretty common still but will probably become collectors items as Marlin slowly disintegrates
G - Guide - 18" barrel
SBL - Nobody really knows. Stainless Big Loop and Stainless Black Laminate are popular guesses though
GBL - Once again, a bit fuzzy. Guide Big Loop is a popular though.
In an 1894, "C" generally means 18" barrel but more reliably, denotes the chambering as 357 Mag. Anytime you see a C in 1894 format it will be a 357.
1894C - 1894 with 18" barrel in 357 Mag
1894CS Same as above but an older designation for the, then newer, cross bolt safety equipped models
18894CSBL Same as 1894C but with stainless black laminate (or big loop) additions.