Texasjack,
Believe it or not, you confirmed that it is chambered for 7x57R ,since it did not extract the rimless case. A 2 3/4" 16 ga shell will chamber in a 2 1/2" chamber, because the crimp shortens the unfired case. When it is fired, the crimp unfolds into the forcing cone, creating an obstruction and increased pressures. This is a point of great controversy among 16 ga users; some insist on using 2 1/2 shells, some advise rechambering, and some use 2 3/4" shells and chance damaging the gun.
I made the comment about the stock, because it shows signs of having been sanded, the color doesn't match the forearm; and as far as the "repair" is concerned, there is a plug showing ( usually to cover a screw).
While I couldn't examine it, the scope seems to be a good one. I don't like to estimate worth of someone else's gun. I can only reccommend you compare it with others that have actually been sold on different auction sites( pay no attention to those that have not been sold for 2 or 3 years). Also Simpson Ltd. recently imported several different types combination guns and their prices are firm prices, they are not an auction site.
My comments about the stock should not be taken as a criticism , but rather as information. In my unsolicited opinion, you should keep this gun and use it,it is a very good and useful gun which will give you many hours of enjoyment.For 7x57R ammo, check out Huntington Die Specilities or J&G Sales.
I hope you find this helpful.
Mike