Fascinating! Hate to complain, but could you please redo the series with the lights turned on?  :-)

I'm guessing one of two things:

(1) Prototype - wonder if it differs in any way from the "production" version? Do you have a clip?
(2) Old assembly of one picked up off the floor by an SA worker?

Certainly isn't one of the trial pieces from the 288xxx period.

Again - fascinating - thanks for sharing!