From the '08 NEC, I've gleaned that the wiring cleat sockets use is only permitted in "industrial or agricultural establishments". [398.10]

The cleat sockets themselves are mentioned again in [410.5], to be installed 8ft or higher from the floor, but no reference to [398.10] is made.

If I were attempting a "mock historical" installation in a resi. setting, what would I do??

hmmm, make them 12 volts?

I second the 12v suggestion. The NEC is sort of funny about exposed terminals. They don't even like them on the wall side of a plug cap, even if you still have the fiber insulator.

I wonder if anyone makes a reproduction that you can back wire and make it look like it is top wired.

12V? Not possible with repro antique bulbs, and the high amperage would make it worse, IMO. We're talking maybe 20 or 30 bulbs around the walls of a room, near the ceiling. I'd guess around 1000 watts total.

*Personally*, I don't see why there would be a problem with this in common sense terms. I'd simply mount the sockets at 7ft (same minimum for equally-dangerous ceiling fans), use a box in the wall as normal, and have some sort of decorative fixture to transition from the box wiring to the cleat wiring.

Since it's only for a 'mock historical' installation I'd talk with the local AHJ and see if I could convince him that it could be done safely. If they're mounted at 7' above the floor he might be amenable, especially if there is adequate code-compliant wiring to serve the needs of the room. Maybe if he can see that there would be no temptation to ever touch or tap the cleat wiring he'd let you do it.

You are talking about something like this?

Yes, that's a cleat socket and there is little to no variation in their form. A simplistic socket with two terminals and two mounting holes.

Here's a small temporary plug-in install. The wiring is one piece, following the one conductor per screw rule.

At least put them on a GFCI. Make the contact unpleasant, not deadly.

I would say GFI and let it be, as long as it is "Temporary".