All of my Glocks are 3rd generation. AFAIK, the 3rd generation Glocks are the only ones that have finger grooves molded into the grip and a rail for a tactical light/laser. The 2nd generation Glocks had only raised panels on the sides of the grips and stippling(sp?) on the front and backstrap on the grip. I don't think they came with tactical rails. The 1st generation Glocks didn't have any stippling or raised panels on the grips. They didn't come with a rail either. There could have been, and probably were, other differences between the different generations. The grip/rail features are the only differences I can think of offhand, and I might not even have those details completely correct. HTH!