Zenith stamped the model number on the back of the cabinet. Looks like it says 8S463. Time to consult the Zenith Oracle:
http://www.oldradios.com/reference/zenith.htm
And the Zenith Oracle says that chassis 5808 was used in the 1940 model 8S463 - sounds conclusive to me!
Schematic is in the 1940 Beitmans which you can download here:
http://www.eskimo.com/~p0lez1/beitman/beitmanhome.htm
ADD A FUSE to this radio! You can hide an inline fuseholder under the chassis. The 6X5 rectifier tube is prone to shorting, which tends to make toast out of the power transformer... needless to say, not the easiest part to find replacements for...