Bill,
Don't hold me to it, but I THINK the differences between the gen 2/gen 3 are the loaded chamber indicator bump on the extractor, a second pin in the locking block, and the rail on the dust cover. I am by no means an authority on Glocks. Started out hating them, as any good 1911 man should, and ended up appreciating them for their performance. I have had a few I let go, but still have a mdl 17/mdl 22/mdl36. They have become my "Go To" guns.
Savage