Jack, according to my books there was no such switch originally. It is most probably aftermarket. Could be for spotlights, a horn or (as in my friends car) an illegal reversing light switch.
Is your switch still connected to wires? Where do they go?
Could the switch be only camouflage for a hole in the dashboard? In some cars the rotary switch for the adjustable shock absorbers (Armstrong Selectaride) was in that position. These shocks weren't very effective and not too reliable and were often exchanged for non-adjustables.
Just my twopence
Frank
