I have a Glock22 I bought from a local guy. He got it as a Police trade in. He needed money for an AK build. He had sent it back to Glock 3 months ago for a referb. It's like new, all refished and new night sights. They glow bright. They are marked,AK(rear) and MH3(front). What are the meanings of these markings? Are they just standard part numbers? Thanks.