Apology and some research
Please accept my apology for what I said about selling the gun. That was uncalled for and I had no reason for it.
I have also been doing some research and have looked at (I think) every known alphabet in the world with no result. Yet, as I look at the pictures, I can see where you get the idea that the lettering might not be just random characters like you see on some "hand made" guns. Nor do the letters appear to be engraved, which indicates that someone made up stamps, a tedious business for a limited production gun. I considered the idea that some of the letters were upside down, but they appear to be used consistently, not in a random way.
I don't believe it is Cyrillic, though. I know Russian fairly well and while there are some letters that could be Cyrillic, many are clearly not. It is not Arabic or any of the Asian languages I can find. I thought it might be Thai, but no dice there, either.