The cartridge shown in Datig and COW is the 10.75x65R Grundig not the Collath.

The 10.75x75R Collath exists, is super rare and is a slightly necked version of the larger cased 11,15x65R LK (which is the same as case as the 11x65R Collath).

Refer Dixon - European Sporting Cartridges (vol 1).