I just traded a Gen 3 Glock 21 for a Gen 3 Glock 19 and when i got home I noticed it had strange markings on the barrel, slide, frame. It has NPv on the barrel, slide, and frame, and AOH on the barrel. It also has Glock Inc. Smyrna GA on the bottom of the trigger guard. I'm sorry if this has been asked before but i searched and didnt see an answer. Can someone enlighthen me on these markings? The serial # begins KVE so thats 02/2009 right? it looks like the person who had it installed an extended mag release but it sticks out WAY to far so i want to change it. Is that something i can order and do myself? And is it worth any more than any other G19? Thanks for any help and I'm sorry if this has been covered before.