Thanks for the feedback w3wilkes. It is actually two horn relays soddered together. They are identical to the other relay in the picture, which I have traced to the horn. I'm thinking you are on to something with this being a potential primitive headlight relay system. I'll be breaking out the multimeter tonight to do some more testing.
I'm also going through 47 years of maintenance and repair paperwork I have on the car to see if anything fits the bill.