Very nice, and remarkable contrast on the 3 Iron Crolle barrels
Dating the proof marks is interesting.
Non Pour Balle appeared pre-1897, then CHOKE next to the bore until 1910
The gun may have been reproved post-1910 with the muzzle constriction of 17.8 = .701 over bore 18.5 = .728. The choke may have been opened as 17.6 would be .693.
It looks to be a non-ejector so should be a No. 1 or 2? I don't know which model has side clips. The Pigeon models were all ejectors.
What is the weight of the gun? If a Featherweight it would be a Special Non-Ejector.
Cornell Pubs has a 1908 VL&D catalog repro
https://cornellpubs.com/product/1150/Almost all the Francotte imports I've seen do have the chamber length in inches
It does not carry smokeless proof, but that was optional (starting in 1891), came with an additional price, and was often not performed on guns intended for export to the U.S.
It was proved for a max. service load of 1 1/4 oz. / 3 1/4 Dram Eq. (1220 fps). Black powder loads of that period ran about 8500 psi and Bulk Smokeless about 10,500 psi (Same as today's SAAMI max).
1 1/8 oz. 3 Drams Bulk Smokeless was 6000 - 8000 psi.
Certainly the wall thickness should be checked and if adequate, in light of the age of the wood, I'd probably stick to 1 oz. at 1200 fps target loads.