CRT's were already to 9" by 1929. This one was 12" (30cm). The high voltage supply in all pre-war sets except the German E1 (first set to use a flyback HV supply and have a rectangular crt) was a simple high voltage line transformer, rectifier and cap. Nothing fancy, but deadly.
The knobs are all functional and can be seen here:
http://www.earlytelevision.org/telefunken.html
Darryl