Ah, I see a 46 which would point to the 8.15x46 1/2 R. Now the "Crown" over "G" is for proof with a solid projectile. The Austrians used a solid projectile for all at the onset then if it was to be proofed with shot at a later stage thru a tube with constriction, Not for Ball was pressed on the tube.

Kind Regards,

Raimey
rse