I still think there's clues to be had from the '64 catalog, but not great clues (like: what's a "chromed saddle bar sleeve"?) There are 2 bikes in there that had tubulars and either "Nervex" or similarly ornate style lugs, and seem to have Durifort fork blade decals. These both have later (maybe foil sticker) graphics, but there are strong similarities to the OP's...and have 3-main-tubes 531. I think the OP's might be a "102" which had Campy hubs, or a "De Luxe", that had Campy derailleurs...but neither had alloy cranks. And, since I'm guessing, I'd say it's a '63...perhaps the last year Gitane used the old graphic down tube logo. All just guesses, but that's my best.