Somebody asked about seeing one of these in operation. Here's my (blurry) snapshot of the DuMont at the early television museum in Ohio.
http://antiqueradio.org/art/temp/DuM...lSovereign.jpg
And their house photo of the same set.
http://www.earlytelevision.org/dumont_ra118.html
It was playing the Wizard of Oz continuously during last year's convention.
A truly amazing set, and it's hard to grasp how mammoth it is unless somebody's standing right next to it.