I have owned an 8x75 which came to me as an action only.
It was a double round top, and featured narrow , tappered bottom metal, making chamabering of another cartridge a real challenge.
One other 8x75 surfaced two years ago, it had been butchered , and I missed the opportunity. Yes very ,very rare.
I would be very surprised if as many as 7000 Magnums were produced, when I get a spare month Ill go through the archive!

Close to topping the rare catagory must be the short /intermediate sloping box.......Im lucky enough to have one.

Best
Eric