No proof mark would have been Paris before 1900 or so, when proving was optional.
However, the 9.3x74R originated after 1900, so it's tough to say what happened here. Possibly a rechambering from an earlier caliber such as .400/.360.
Belgium, St Etienne and UK would have been proved.
Nicolas Guyot, 12 rue de Ponthieu, Paris. I have seen stuff from the 1880 time frame all the way to 1930 or so.
He is one of my very favorite Parisian retailers. Double rifles are very rare indeed.
He often used Whitworth Steel for the barrels.
I would say that the Parisian makers became more or less all retailers around the 1900 time frame.
Pictures will help.
Best regards,
WC-