Prewar Zenith consoles are about the only ones anyone will pay anything for, and this sure sounds like one. The REALLY desirable ones are the high tube count models, 12 tubes and up. Think thousands in that case. Most of the black dial ones are in the hundreds and up, depending on model. I'd snag it and ask questions later! The 1939 models and after are less desired, and a pain to work on, as they are wired with rubber insulation which turned brittle and crumbled away YEARS ago... will need COMPLETE rewiring. Still probaly worth it...
The model number is usually stamped on the top edge at the back, though if not, there's usually a chassis number that will narrow it down to a few models. First part of model number is number of tubes. Second is a letter (S: shortwave, H: FM, D: AM only, R: Record player etc.) Next digit is year: 1: 1937, 2: 1938, etc. Last two digits are model, usually the higher ones were more expensive originally.
So 7S232 is 7 tube, shortwave, 1938, table model.
Ask the Zenith Oracle if you get a model, chassis, or serial number:
http://www.oldradios.com/reference/zenith.htm