Czech 7.5 x 60 Experimental

Hello All,
In the book “Czech Firearms and Ammunition” by Dolinek, Karlicky and Vacha (page 89), the authors talk about a cartridge under development in 1947-1948, the 7.5 x 60. It was to be used in repeating rifles. There were two rifles in development, the KASKOL developed by Ing. J. Kyncl and the P model developed by Ing. F. Holek. The 7.5 x 60 was not used and was replaced by the P6 model in 7.65 caliber. Neither rifle was adopted.

What were these two cartridges? Does anyone have photos and dimensions of them?



(please pardon my lack of proper diacritical marks on the names)