I recently bought some 8mm Mauser brass from a member - with the above headstamp. These primers have to be knocked out with a 1/16" punch and several strikes with my kenetic bullet puller. My Hornaday dies wouldn't touch these primers. On several the primer was so tight it didn't move and punch punched a hole in it. In addition they are very hard to size, I would guess machine gun fired.
Who was making boxer primed 8mm brass in '42?