A nice find!
Yes, 1930s by the looks of it. A battery eliminator and a very useful one indeed as it provided HT of 120/150V plus 80V, screen grid voltage, grid bias from 1.5 to 12 Volts, and variable LT voltage. The only voltage that was critical was the L.T, hence, it was metered. I guess most pre-war battery radios used either 2V or 4V heaters.
Rather more veratile than the more commonplace Ekco K12 battery eleminator. It would make a nice restoration project, and if restored and made safe would be most useful for powering pre-war battery sets, and no doubt the battery version of the Wartime Civilian Receiver.
These two forum links might be of interest. Though not the same model, the neatly drawn circuit in post #1 at the first link appears to have some similarities:
https://www.vintage-radio.net/forum/...ad.php?t=55096
Split from this:
https://www.vintage-radio.net/forum/...ad.php?t=37054
Hope that's of interest.