vixen,
What you are describing is a O/U CAPE GUN, which was very likely made in Austria or Germany. - VERY FEW 12 gauge shotguns were made in Europe for "domestic use" in the pre-WWII period, though any number were made for export to Africa, British India & the Western Hemisphere.
To me, the most important thing before firing either barrel is to have the caliber/gauge/condition CAREFULLY CHECKED by a competent smith who KNOWS European combination guns & their "quirks".
(There are at least 2-3 other possibilities in .25 calibers for the rifle barrel, other than the .25-35WCF & more than one "case length" for shotshells, too. - Also, do NOT believe the marking on these European guns; remember that Europeans were just as likely to have "modified" weapons to non-standard calibers as USA owners are.)
Inasmuch as I've NOT seen the cape-gun, nonetheless, I would guess that it's worth 1,000-2,500 USD at a fair retail price.
yours, tex
It's actually not a cape gun. Cape guns are SXS, not O/U. It's a BBF (bockbuchesflinte). In German a cape gun is a buchesflinte.
The 12ga will be chambered for 65mm ammo of a low pressure. You should do OK using 2 3/4" light trap loads. They didn't chamber these guns in 2 3/4". The maker is one of the very best, and the price is good. Be sure to take off the forend, and with the gun closed sans forend shake it while holding the grip only. If you feel any movement it has a loose hinge pin, which could be costly to remedy. But, at that price if all else if very good the gun could still be worth the price.
I'd love to see some pics of it.
