01-23-12: LewmLew, you might find this page to be of interest. Note that each set can be clicked on to expand the photos and for more information.
I used to listen to The Lone Ranger on a black Zenith tube radio, when I was a child in the early 50s. I never realized it dated back to the 30s.
If it was a tabletop set where the height was significantly greater than the width (referred to as the "tombstone" style), it was almost certainly from the 30's. If it was wider than it was tall, it may have been from the 40's or from the late 30's.
The 1930's black dial Zeniths are very popular with collectors.
Best regards,
-- Al