A friend of mine recently inherited a drilling. It was apparently a wartime bring back from his great uncle's estate.
It looks to my eye like a Suhl gun, but there is no manufacturer's signature that I can find. The barrels are stamped "nitro" and there is the usual assortment of proof marks and other characters. It is SxS 16 over a rifle barrel marked "8.8mm" with no length designation I can see.
It's a hammerless boxlock, with nice game scenes, and horn trigger guard, butt plate and grip cap. Any thoughts on what the rifle chambering is? Any other random thoughts?

Undoubtedly a 9.3X72R. Look for numerical characters on the underside of the barrels to identify the proof date. Most of the time the date will be in the form 434, which would designate April, 1934. Rarely you will see it in the form 4/34.

He is right; metric caliber designations like this usually refer to the BORE diameter rather than the GROOVE or bullet diameter; hence the 8.8mm marking. And by far, the most common 9.3mm cartridge for that era was the 9.3X72R. About like a 35 REM in power. I had a JP Sauer 16x16 over 9.3X72R and used it to hunt with when I was stationed at Ft Stewart as everything was in season at once. Squirrels, deer and hogs.

I would suggest you do a cast of the chamber and slug the bore. It might be a 9.3x72, but there are a couple variations of that cartridge. There are also a bunch of similar rounds that were chambered in drillings, cape and combo guns. The 16's are probably 65mm instead of 2 3/4. That's a lot easier to resolve, since you can get short shells from a number of makers.
Bfly

I reamed my chambers to 2 3/4; 16 ga shells are hard to find nowadays in any length. I remember when 16 ga was a strong number two seller right behind 12, and 20 ga was not used much.