This is the insulator for the horn contact for the Ford models below.
It pushes into the steering wheel, and is often missing.

1960, 1961, 1962, 1963, and 1964 Falcon
1960, 1961, 1962, 1963, and 1964 Mercury Comet
1960, 1961, 1962, 1963, and 1964 Fairlane
1963 and 1964 Galaxie
1965 Mustang with generator
1961, 1962, 1963, 1964, 1965, and 1966 F-100 / F-250 except 4WD
1967, 1968, 1969, and 1970 F-150 / F-350