Two different Avanti sedan prototypes were designed by Loewy's team - the black, formal roof sedan that was the puzzle car, and fastback sedan that more closely resembled the Avanti coupe that entered production. Each sedan prototype, constructed by longtime Loewy favorite Pichon Parat had two doors on the driver's side, and a single door on the curb side. The fastback is the gold example behind the black car in the picture I added. A better look can be had here: