I don't think I've ever seen a French double that wasn't proofed at either St Etienne or Paris, so the fact proof was not "obligatory" does not seem to have made much difference--unless you happen to find that rare exception (which I've never seen): a French gun without proofmarks.
Some of the photos are a bit blurry, and although some French barrel flats contain enough writing to constitute a short novel, this one comes close to being the all-time champion--and includes some expressions I've never seen. Here's what I can tell you--and as Raimey said, a lot of the stuff on the flats is basically "advertising":
canon de surete--safety barrels
double epreuve--double proof
canon Fanget--Fanget made the barrels (I've seen Fanget barrels on a lot of French guns)
qualite super whatever (can't make out the last word)--super quality something
acier inexpolisble--the steel won't blow up
crochet encastre--has to do with the type of action
choke rectifie--regulated chokes (but they don't tell you what they are; never do on French guns)
fermeture integrale--integral closing (has to do with the lockup, but that's one I've never seen before)
portee garantie--the range is guaranteed (but they don't tell you what the range is)
Crown over a V--not a standard French proofmark; any guesses, anyone?
Spirobloc--either has something to do with the action, perhaps like "Helicobloc" which is seen on many French guns; if so, it's sort of like a Scott spindle in reverse--or else designed by Spiro Agnew
Gatimel--we had one of those show up recently. Big sporting goods store in Marseille, apparently still in business. Not the maker of the gun.
I have never seen the dragon mark before.
The only really important things of all the above are: 2 1/2", double proof, and French.
