This is a tiny carbon arc rectifier using two Tungar tubes.
Input is 120VAC single phase. It was made by Strong Electric
for National Theatre Supply and is the companion to a small arc
lamp (approx 8" reflector). Yes, it still works although I have
not fired it up in years.
Here you get a better look at the Tungar rectifier tubes.
These were also used on larger units (6 for a three phase unit).
(It's not glowing in the photo--it's just glare off the shiny
coating inside the glass. They do light up in use, though.)