I don't know if the model number variations were actually stamped on the radio and/or cabinet, or if they only existed in catalogs, but:
5S237: Wood.
5S237W: Bone White.
5S237Y: Ebony.
Cooljjay may be correct about the veneer. It would be logical to assume that if the original was painted instead of stained and lacquered, they wouldn't have wasted a quality veneer under the paint.
Since you didn't say that your model number included the "W", I would certainly go to the trouble of carefully stripping off some of the paint, and taking a look at what's underneath. If it's walnut, walnut is an open grain wood, which means that the paint will have gotten into the grain, which means that getting it out is going to be a pita. You'll need a stiff-bristled brush to go along with the stripper, and a lot of patience.
If you're going to repaint, that's easy. If it turns out there's walnut veneer under the paint, and you decide to try to restore the finish, you'll need to go here:
http://www.antiqueradios.com/forums/...2281e938f1f77d