"Eunice Jean" a 66 F 100 named for my mother has no horn ring. Did all 66s have one? mine has the center horn button but no ring.

 

It appears to be a custom cab option but I could be wrong. My 63 std cab had just the button while my 56 and 66 custom cabs have the ring and button. Also some buttons have the gear and lightning bolt while others have the ford ovel.

JJ