Well, you are pretty close in your estimations of the rifle. It is indeed a Yugoslav re-worked Kar98kicon. The numbers on it do match but are not of German stamping- probably from the Yugos. The receiver ring would have been "sanitized" during the rework and so all of the markings being gone is common place. As for who made it originally... that is a bit more tricky. I wish I could tell you more about it, but you seem to have it mostly sown up... I would have to guess for value... somewhere in the $300 range, but that is my humble opinion and there might be something I missed to add more. For that, I would let some more "senior" members check out this thread. Good luck!