This vintage of Zenith table radio is very late in the game; at, or very nearly the last all-tube radios from Zenith in Chicago. They are getting harder to find:

http://cgi.ebay.com/Vintage-Zenith-AM-FM-Tube-Radio-Works_W0QQitemZ120123012716QQihZ002QQcategoryZ3803 5QQrdZ1QQcmdZViewItem

Funny that it would have BOTH model numbers (X316 and X318?) on the bottom. I thought the different numbers gave cabinet color?