Mike,
I don't have experience with the two less common 8.2 cartridges, but I do have experience with 8x50R. I also consulted a couple of Austrian gun catalogs from the 1920s. And you are of course right about 8.2 not being a name but rather diameter; maybe I should have written "name". Bottom line, I basically wanted to say that I agree that this drilling is probably chambered in 8x50R Mannlicher. But we can't be sure without a chamber cast of course.
With kind regards,
Jani