I have FOUR of these at this time now. Excerpt from the 1st eBay listing:
A pair of 1940s Theater amplifiers made by the David Bogen Co. and distributed by National Theater Supply. Rare 125 w. Bogen theater tube amplifier-monoblock pair. 1940s -National Theatre Supply 807 output NTS-1125. 125 watts RMS per monoblock amplifier using 807 output tubes in class AB2 push-pull. The 807 is a remarkable tube, similar to a 6L6, but can take over 800 volts on the anode and is classified as a transmitting tube. Rugged, almost indestructable, yet has very pleasing sonic characteristics. two 6SN7 as drivers, 6SL7 front end voltage amplifier. 5R4 rectifier for the 800 volt power supply. 5y3 rectifier for the front end and screen 300 volt power supply. 5 transformer on each chassis- anode and screen HV,filament, input choke, output , and driver (audio choke coupled driver). Wired for 8 ohm speakers. (*can be wired for 16 ohm)---HIGH VOLTAGE PRESENT AT 807 TOP CAPS-DO NOT OPERATE WITH COVER REMOVED-
Similar Bogan amplifier listed as a GO-125 in the Rider Public Address Equipment manual Vol.1. The GO-125 only had 70v line output taps.
* These NTS-1125 have two 16 ohm taps, 140v tap. both 16 ohm taps are strapped for 8 ohm speakers as wired now.