If found these in a box of goodies I picked up some time ago. I've probably had them for a few years now but finally dug through the whole box of parts. I found these, two Stronglight 93 cranksets, several French bottom brackets, a Stronglight headset, and two sets of Mafac 'Racer' brakes and levers. Not to mention a pile of old Simplex derailleurs both new and used. Most of the parts were early 70's at best, some maybe even older. It took also took me a while to figure out what some of the fuzz was in the box, but it turned up to be a disintegrated set of old sew up tires with the tubes removed. The threads are so rotted the tires fell part to the point they resembled corn silk in a box.
Anyhow, these are different from any I've seen before, the shoe clamps are larger than those on the Racer variety, and the straddle wire is double ended. They are marked only 'MAFAC' with no other engraving.