I'll start by posting the pictures of your Robust and will offer up that the model 222 was made from 1946 to 1980 per Myorkas' book. FAB500 might give more information.
-- Manufrance Robust
-- Double Proofed at the factory as a finished arm. This from Fab: after 1926 manufrance ceased using the customary saint etienne proof house, and ran their wares through an in-house facility.
https://www.doublegunshop.com/forum...;Main=39635&Number=595336#Post595336. . . . .- one arrow thru target = 850kilos = single proof
. . . . .- two arrows thru targets = 1100kilos = double proof
. . . . .- three arrows thru targets = 1300kilos = triple proof
-- Canon Frette - is the classic "stepped" or "sleeved" (In the sense that an artillery piece has "sleeved barrels") MF barrel.
-- "Hercules Steel"
-- "The rifled barrel" ("raye") probably has striations on the last few inches of the barrel: I believe it can spin a ball or act as a spreader for shot shells (barrel used for Becasse?) but will let others chime in.
Check out this line - which is perhaps the finest explanation on the entire internet of the French practice of shallow groove refiling in a shotgun barrel, its result on shot-shell patterning and on bullet/ball accuracy.
https://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=587581&page=1and by the way, I don't see a "222" but there is a "32-S" (1930-31)