" All those proofmarks don't appear to be Belgian."
Sorry, Raimey, but I can see only the usual Liege, Belgium blackpowder proofmarks! On the action flat there is the "Perron", the symbol of the City of Liege, and a "V under star", a Belgian inspectors personal stamp. Under the rifle barrel there is the "EL" blackpowder proofmark, The "ELG in oval under crown", the Liege proofhouse acceptance mark in use from 1893, and the "R under crown" which in Liege marks proof of a rifled barrel. "8.8"mm is the correct bore (not rifling or bullet!)diameter for both the 9.3x72R and it's forerunner, the 9.3x57R aka .360 BPExpress.