Back in the late 1980s a boat load of C96 and M1930 style pistols were imported from China. People Liberation Army was dumping junk to generate foreign currency. Long barrels and Bolos from Mauser, Astra and Shansi were available. Some came through almost new but most were pretty beat up and some were truly terrible roached out, rusted junk. Calibers included 7.63, 9mm Parabellum, 9mm Mauser Export and .45 ACP. They were somewhat common at shows at the time. (I still have a matching Bolo with no lands and grooves and several Chinese made leather and wooden holsters.)
I dug around in my files and found brochures from three importers/rebuilders: Antique Arms Arsenal, Mentor Arms Co. and Oyster Bay. There may have been others involved. These three suppliers sold "as is" pistols, parts, and accessories such as holsters, fitted cases, cleaning rods, new wooden grips as well as offering services to re-barrel, re-line, re-build, re-finish/re-blue and engrave to suit. Antique Arms brochure shows new made custom length barrels up to 16" and offered a Mauser Carbine made up from parts. Workmanship wasn't bad but definitely not original quality.
I can't tell for sure from the pictures but I think this example is one of the refurbished Chinese imports. More pictures would help. Recommend checking for import marks and any commercial marks.