Slightly bottleneck at the very end 10,75x68R Mauser was common for DR, combos and drillings. It was much slower, than rimless version 10,75x68. Grundig and Collath sounds odd for Belgian DR. Moreover 10,75x65R Collath, known as Tesco-Hulse was with straight case. Also there was Mauser rimless 10,75x63 and Ihave no idea about the same with rim.

Geno.