Classic French bike built with unlabeled non-descript tubing, how's that? Some of them ride really well due to good geometry. Yours looks like a Jeunet 620, unlabeled tubing with brazed-on cable stops on the top tube, but very similar geometry to the 630, which was full 531 with plain Simplex ends that used cable clips for the rear brake cable. My favorite example of this sort of bike is my Liberia, which appears to be the very cheapest model they made, but tricked out with 27-in wheels for the U.S. market for that brief time during the bike boom when distributors were grabbing everything they could from regional and smaller makers to feed American demand. Mine started life as a $100 college campus bike sold out of a shop adjacent to the University of South Carolina. The tubing appears to have a wall thickness of around 1.0 to 1.1 mm, though, which isn't too shabby, and the geometry makes it corner like a much more expensive competitive bike. On paper, it shouldn't ride this well. Replacing the rusted-out Saminox steel rims with some old Weinmann alloy units helped.