Most of these are in chambered in16ga. Measure the chambers: I believe it’s for a short 16 ga cartridge. Although you can use modern 16:ga ammo in it, I’d only use low pressure ammo from RST.
Drillings were in demand in continental Europe and Africa for their 2 in 1 form in the first half of the 20th century. A good deal of their market didn’t have the wherewithal to own both a shotgun and a rifle.
I wonder whether that gun went to Africa because of rifle caliber: 9.3 x 72S is like a 375 H$H for double guns. The 375 H&H was primarily chambered in bolt action rifles (although a rimed version was offered for double gun use).
The 9.2x72R is more powerful than needed for most continental game. African game offers larger and more dangerous game than that found in Europe so a break action gun chambered in a cartridge that’s equivalent to the 375 H&H would have been welcomed in Africa.
I agree it’s probably a guild gun, built in Belgium or Germany.
If I had the chance to examine it in person, and I found nothing that concerned me, $1,000 isn’t out of line, especially with the ammunition that’s part of the deal. That ammo is pricey.