that gun does offer some challenges, it would be useful if owner could post photos of the tubes in front of the flats, and of the "watertable" (i know that term irks some...)

it starts out quite normally;
cal 16 normal = 65mm chambers
demi-choke on right = half choke - which to the french means 25-30 thou
choke on left = full choke - which means a bunch - 40-45 thou
arme finie = proved in finished state
fabrication mecanique / canon frette = the mono-block barrel knitting of manufrance.... as evidenced by the obvious step at the front of the monoblock, where the tubes insert.
acier = steel - but here without any of the superlatives the french favor....which signals that it is a lower grade gun.

but here it takes a twist;
epreuve = single proof
pression850kilos = single proof - at the manufrance in-house facility
arrow thru target over PT = single proof, using powder T - again at the manufrance factory

fab500 gives us a very useful entry from a french text about manufrance that helps answer numerous questions... https://www.doublegunshop.com/forum...;Main=39635&Number=595336#Post595336
after 1926 manufrance ceased using the customary saint etienne proof house, and ran their wares through an in-house facility.
one arrow thru target = 850kilos = single proof
two arrows thru targets = 1100kilos = double proof
three arrows thru targets = 1300kilos = triple proof

but these barrel flats lack two markings that manufrance guns always carry - "always" is kinda like "never" - it's a tricky word....
look back at the gun that started this thread; on the flats nearest the breech there's a mark centered under each chamber (and oriented parallel to the bores instead of perpendicular)....the crossed cannons bracketed by M & F, and the circled MF trade mark.

those marks are conspicuous in their absence - everything about this gun says field grade manufrance Robust - built after 1926 - maybe pre-war, maybe post-war. the fact they are absent leads me to the assumption that the gun was built and proofed by manufrance - in the finished state - but wholesaled to someone else, to be sold in france - but without proprietary markings by manufrance.

best regards,
tom

"it's a poor sort of memory that only works backwards."
lewis carroll, Alice in Wonderland