Hubertus was a German manufacturer of rifles, combination guns and drillings and I believe are no longer in business. The 9.3X74R is a rimmed cartridge which is very close to a .375H&H. The 6 X Kahles is a top of the line German scope.
You may wish to contact the German Gun Collectors Assoc for more information at
http://www.germanguns.com, Email: jaeger@valley.net and
phone 603-469-3438.
I believe that you also can purchase a reprint of Hubertus literature through the above association. I hope this helps.