"I think they represent stolen guns."

You should not have made this statement.
As I stated above, there is evidence that the AF transferred some to PD's.
How many 1911's and 1917's have we seen butchered by grinding off the "US Property" stamps because some idiot thought it meant it was stolen?

The gun pictured here came through a pawn shop, meaning the number was run through the computer by the police department. Had it been listed as stolen, it would not be seen here.
So, you cast doubt on every AF Mod 15 out there, whether released legally or not. Researching the paper trail on military weapons is nigh on impossible. It probably exists, but having the time and resources and access to find it is seldom possible.
Therefore, it would be better to assume one is legal till it is proven otherwise. Your statement does us no service.

__________________
Regards,
Lee Jarrett