I can't find anything about the Clarion control head.
Here's a Ford control to show you something similar.
That would connect to something like this, probably mounted on the firewall. The volume and tuning cables were metal, like speedometer cables and the actual "pots" are down on the radio.
I've been looking for Clarion radios and found a few table top radios from the 30's. I can't find a good history of the company though.... Wikipedia shows it as a Japanese company started in 1940, and not using the Clarion name until 1970. I'll bet they either bought Clarion or the rights to the Clarion name around then.
I remember them in the 60's as an aftermarket supplier of tape decks etc.