This will probably provoke some derogotary comments but I believe that had the second World War not commenced when it did, the germans would have taken over from the big british gunmakers in the production and sale of double rifles. They were cheaper and very very attractive hunting arms. Prior to responding take some time to search the web or physically viewing some of the guns made in the 1930/40s. Absolutley magnificent in presentaion, high relief engraving the norm rather than the order, high tolerances etc. Cartridges produced were usually duplicated mm to inch such as 10.75 x 68 to .425Westley Richards and there are several others. Not always copies of current english cartridges, sometimes the other way around.
No, I am not of german origin, yes, I have owned several british doubles and unfortunately only fired/borrowed some beautiful german doubles and owned a few drillings and combination guns and single shots. (wish i still had them)
cheers