First of all, I'd like to say hello. I just traded in my glock 21 for my Steyr m9a1, already was a big fan of Steyr having an AUG and a Scout. So I decided why not complete the family. Anyways I was wondering about my pistol and when it was made, its letters are ZWM which unless I'm misreading something would be June 2015. SAI Bessemer Alabama. Just curious what gen it would be, if its 2015 would it be Gen 4? If so I'm wondering why it doesn't have the pin under the rear sight post. All serial numbers match on frame, barrel and slide. Thank you!