Try searching the forum.........I saw someone post a nice article WITH pictures and described them in details.........gen one, two, and three. Then I read somewhere someone claiming a gen four. I know in the article the person was slightly off, because they have a picture of a gen one and that was not the same get one I have. Mine does not have a LOCK SAFETY on the slide and I know for a fact mine is gen one. Also, mine is the DAO trigger while the other gens are DA/SA.
I will see if I can find the link for you.