This started probably back in the bike-boom days when a frame with these special dropouts showed up at the LBS.
They captured my fancy but not my pocketbook.
When, some decades later a large internet auction site began operating I bought this frame - and then another, as it showed up shortly after and was better (more on that frame in a separate post-to-come).
Both frames I had shipped to and stored with a relative in the US, and when a few years later I later visited they came back in my luggage.
They both got painted, then languished for more decades (nicks and scratches); and recently the top of the pile has shrunk down to their level.

As far as I can tell this was an Interclub, it takes a 25mm post.
The frame weighs 2540 gm, the fork 840 gm, so it's not a real lightweight.
As built it's well under 11 kg.

Everything is french except the saddle and consumables - freewheel & chain, cables and housings, bar wrap, top-tube clips, and tyres.
Mafac Competition brakes
Not sure of which Mafac levers, they have the Course 218 adjusters and hoods, but solid levers (and the nipple seat is unslotted).
Hubs are Normandy, the rear a bit of a bodge; a long time ago it had an italian freewheel forced onto the french threads, with predictable result - so I unlaced the wheel and cut english threads on the other side.
Rims are Fiamme red label.
Stem is Ava, bar is Guidon Phillippe, wrap Benotto.
Seatpost is Rubis 983.
Saddle is just something stuck on there for testing.
Stronglight 93 crank, Atom pedals.
Shifters are Simplex retrofriction.
Rear mech is Simplex SX410, front is SJ A102.
The tyres are also just for testing, likely 40 years old...

I quite like riding this, it seems a little long and slow turning, but straight on it does go when you tell it to.