I cannot say for sure but it does have longitudinal scrape marks that suggest it went through a full length sizing die. Since it is an early pic I would not be surprised if it was made with a WBY .460 case. I like the design. It should feed and extract well. Operates at low pressures perfect for the African climate it was designed to hunt in. Has plenty of remaining velocity at 100yds+ for good penetration and would fit in a standard M98 with minimal metal removed from the bottom locking lug shoulder. It also carries the name of one of the most if not the most prestigious company in gun making history.
There are cases manufactured in the States by Quality Cartridge and available through Midway for those who want the correct head stamp.