vangulil,
I suggest you examine the drilling closely for waffenampt stamps that indicate issue to the Luftwaffe. These drillings were chambered in 12ga and 9.3x74R, which was not the most common combination, at the time. If it is a Luftwaffe drilling it would bring a good price, especially if complete with its case and accessories. The first thing to check would be the make, if it is not a Sauer, it is not a Luftwaffe drilling. The booklet put out by Pa. Fish and Wildlife may have the answer to your question. I also find 12 ga. drillings much less responsive than 16 ga.
Mike