From the TV History website:
I'm afraid the value is not great -- under $100 in my book if the picture tube is good. 21-inch consoles from the mid-1950s are not in much demand with collectors.
If the picture tube is shot, then the value is greatly reduced because nobody in the world can rebuild them any longer, and you might have to spend $100 for a replacement.
You need a picture tube tester to tell if the tube is good enough to use for everyday watching. You could contact an area radio/TV collector club and ask if someone there would lend you his tester or meet you somewhere to test it. Here's a list of US clubs:
http://antiqueradio.com/clublist.html
Absent a CRT tester, about all you can do is check the tube's filaments with an ohmmeter to see if it is burned out. This article explains how:
http://antiqueradio.org/FirstStepsInRestoration.htm
If the tube filament is burned out, then the tube is shot, end of story. If it is intact, then you need a CRT tester for the rest of the story. It might be nearly as bright as a new one, or it might be so dim that you couldn't bear to watch a program on it.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html