Hello Alex, and welcome to MTo!
I am not an expert in 108 mm SAKs but I'll take a stab at this. I agree that something is a bit fishy here. I looked at pictures of my own 108's (GAKs, Safari's, Troopers) and they all have the small-v VSSR tang stamp that you'd expect.
I also have a 108 GAK that I returned to Vx a year or so ago for repair after one of the springs broke. I can't remember now if they replaced the blade on it in addition to the spring, but I'll check when I get home. I'm thinking they didn't but just can't remember for sure. Somewhere on MTo there's a thread on this project.
I suppose if you sent a 108 back to the factory for repair of a broken off blade they must still have replacement blades available and I suppose further that those replacement blades would have a modern tang stamp. And if it were me, I wouldn't be too concerned with a factory repair. So your GAK has had a return trip to the motherland to be reborn; who cares, right? But if I knew that the knife had been modified by someone into some kind of Franken-GAK then I'd probably care a little more about it and give the knife a sidelong glance whenever I walked in the room. Probably the only way to tell is to remove the scales and examine the pins and collars holding it all together.
I'll have a look and see if I can find my repair thread, which should have some good before and after pics.
Kind regards,
Myron
PS, forgot to add that the factory did replace the scales on my GAK when I sent it in. They're indistinguishable from the originals except that they are new. So this would also support your theory of factory refurbishment.