Originally Posted by FBinNY

I believe you're describing a Kool Stop quick cam. They no longer make these, but what they were were a system where you replaced the lever of an internal cam QR with a hex hey, and carried the handle separately. The KS version even had a pin in the middle of the hex nut so you needed a hollow 5mm (or was a 4mm) key, and a standard key didn't work.

These were around in the Seventies, and KS didn't invent them so there were a few sources. Note that they only work with the typical internal cam levers of the era, like Maillard and Campy.

I might even have a few left. I can look around if you wish.