Yes sir, beetles. Same beetles that eat powder horns.
Krupp never made a sporting arm in their existence. They made the steel the barrel is made from. Laufstahl translates to "barrel steel." The shotgun barrels were made from steel made by Rochling.
The German firearms industry up until WWII was still largely a cottage industry, much as the British firearms industry. The Germans had and still have a very defined apprenticeship/journeyman/Master gunsmithing program that takes about 6 years to complete. I don't know about today nut between the wars if your "store" sold firearms, by law you had to have a Master gunsmith on staff.
What makes you say it is a Trumpf? As I understand it "Trumph" is the 3 bite locking system, not a particular model as there is also Trumph double guns. Generally, models as we think of them didn't exist until after WWII. That was an American thing. Drillngs were generally known by their barrel/cartridge configuration.
Suhl is a town in the gun making district of Thuringia, Germany where there was a proof house and where your drilling was proofed. NITRO in block letters confirms that. Had it been proofed in the neighboring town of Zella-Mehlis nitro would have been in script. It appears the rifle was proofed with a 15 gram, steel jacketed bullet. That's 231 grains.
The circled 12 indicates it was originally 2 1/2 in. chambers. You need to have them checked as many have been lengthened....but not all.
GENERALLY, 7,8 x 57 is the original 8 X 57 Mauser from the 1888 Commission rifle and has the .318 groove diameter. The "R" stands for a "rimmed" 8 X 57. The "new" 8 X 57 adopted in 1905 by the German military is generally believed to be stamped "7,9 X 57R" and has a .323 groove diameter. They are the same case. The ONLY way to remove all doubt is slug your bore. A chamber cast wouldn't hurt either. Some folks did some really stupid things to those old war trophies, which yours almost certainly is. I have a few in my accumulation. NEVER assume what any old, foreign firearm has stamped on it is correct....and you can ask me how I know that. .323 bullets are easily swaged down to .318 and data abounds, just start low....and in deference to the age of the gun, stay there. The proof mark pictures leave a lot to be desired but, I THINK I see a "536" or "636" that might be May or June of 1936 as date of proof. Though the parts might be several years older as they sat on the shelf for perhaps decades, the date of proof is generally considered the effective date of the firearm. Cleaner and more thorough pictures are needed.
It is entirely possible that a Meffert married a Kreighoff which would make the families related but the businesses never were, so far as I know. It is vastly more likely they used the same supplier AND, the "style" was shared among a bunch of makers. I doubt Kreighoff or Meffert ever made a firearm for the other. Meffert is one of the oldest gun making family/firms in Germany, dating I believe to the late 18th century. At one time I had a Meffert drilling on a Dural receiver in 16 X 16 over 7 X 57.
12 bore drillings were not very common before the war and generally are not as desirable as the more delightful handling 16 bore. I've never picked up a 12 bore drilling, old or new, that didn't feel "clubby" when compared to the svelte 16's. They just get too heavy....awkward feeling. And, that's a matter of taste....but a lot of drilling users share that taste.
This site might be of interest. Dispense with you preconceived notions of American firearms manufacture.
Dietrich Apel and the Foto Gallerie Suhl Waffenkunst or Gunmaker’s Poster Project – German Hunting Guns