1965 Dodge Dart Steering wheel.

Strange.....! I've never seen a 1965 A-body with a horn button.
The cheapest 1965 Valiant V100 and Dart all had the half horn ring. Valiant V200 and Dart 270 had full horn ring as an option and finally Valiant Signet and Dart GT had full horn ring as standard. Re Valiant I might be wrong on the Signet model.