Looks like an old version of the rear-projection sets that are popular these days. A modern "big screen" television uses 3 picture tubes, red, green, and blue, that are focused on a single screen. Most projection sets these days have the tubes mounted vertically and they reflect off of a mirror in the back at a 45 degree angle onto a vinyl plastic screen. On the inside of the plastic screen is a fresnel lens, and on the side that faces the viewer is a diffuser. These sets require extensive convergence setup at the factory, and sometimes need adjusting after they make it to the end user's location to make sure the three pictures produced by the CRT's blend together perfectly. The picture tubes themselves are rather small, only about 6-8 inches in diameter, but are driven extremely bright by using a high-voltage power supply producing over 35,000 volts. (a normal 8 inch monochrome CRT needs only about 10,000 volts to make a nice sharp picture). THese CRT's are cooled with a clear glycol coolant that surrounds the top of the picture tubes. Lenses are then mounted to the face of the picture tube to help focus the picture on the screen.
This television is one of the first applications of this technology. Back in 1947 when this set was manufactured, 12 inches was about as large as you could go on a direct-view television. The projection screen on this set, although about average size for a direct view set today, was huge for that era. Of course the only way to produce a picture that big was to project it from a smaller tube, which it does just like modern big screens. It drives the CRT with an unusually high voltage to produce an ultra-bright picture. The CRT is mounted vertically, and reflects off of a 45 degree angle mirror. I imagine since transparent plastics weren't avaliable in that time that this set uses a glass fresnel for the screen (read, VERY heavy!). I am not sure if the CRT in this set is liquid cooled like the modern sets or not. If it is, I imagine by now the coolant needs to be changed.
On most modern sets, the coolant gets rather cloudy after about 10-15 years of use making the viewer think the CRT's are bad because the picture becomes dull and blurry, and is the cause for many people getting rid of these sets when they are still good!
This would be an awesome piece to have, and I'm really tempted to drive up there and pick this thing up. It would be a REALLY nice piece to add to my collection of vintage electronics, especially since I deal with projection video technologies everyday, it would even be a nice thing to display in the lobby of my shop!
