The problem is that it was dropped on the preselector knob, breaking the capacitor inside. This is not an electrolytic capacitor like I mentioned before, it's an air variable capacitor. You've probably seen them in old photos. It has stationary vanes of metal with others that move in and out. As you turn the dial, they mesh (but don't contact) more or less, changing the capacitance.
Here's a picture of a single one I found with an image search, the one I need has two (I think identical) sections on the same shaft.
I have a manual for the radio which I was able to download and it shows the capacitor on a schematic (wiring) diagram, but does not give any information about it. My guess is that it is a 365mmf air variable capacitor as they were commonly used in AM radios of the time.
The good news that the radio works on 7mHz, which was the band where the capacitor was set with minimum meshing of the plates. I moved it there by hand. Unfortunately it does not work on any other band.
Any information as to what it really its, a source for or a replacement, or a donation of one would be gratefully appreciated.