Dana,
You need to figure out what caliber the rifle barrel is chambered for. Raimey may help with that. The issue is condition of the bores. The shotgun tubes are almost sure to be 16ga. I have a similar gun:
So, I have some idea as to values... They are fun guns. Good in grouse cover because of the short barrels. They reflect the needs and style of German hunting.
You can do a chamber cast to help figure the chambering. From there you can have an insert made up in 22 Hornet or perhaps 30-30. You can also get inserts and shoot 20ga shells.
Pete
