Very weird…
I saw a DP-28 in moscow a while back too, I only assume playtesters and developers (or bots) get issues them? If I knew how to upload a photo I would prove it 
There were reports of looting the pzb 39 in Moscow a while back as well.
So these are either special accounts, or another drop glitch where some weapons sometimes morph into similar weapons when they’re dropped.
The pzb 39 existing is odd, though, as there’s no functional difference between it and the 38.
That’s what I thought… Because they aren’t available for every one…