Hmm...I just picked up a copy of the Standard Catalog of Smith & Wesson, 3rd edition. According to The Book:

06 = 6-Shot
A2 = Single Action/Double Action
LG = Large Frame Size
GR = Rubber Grips
BF = Full-lug Barrel
SA = Single Action
SR = Red Ramp Front Sight
FS = Stainless Frame
CS = Stainless Steel Cylinder
ZS = Satin Stainless Finish