Duster Rear-Defroster/Defogger?

Also available were the Sure-Grip differential, hood scoops (Dart, Demon, Demon 340), FM radio, a rear-window defogger (on all models), a manually operated, soft folding sunroof (on the Dart Demon and Demon 340), power steering (using a roller-type pump for greater pressures and more boost), variable-speed wipers, electric washers, tinted glass, and many other options including a variety of radios.

I got this from a history page,You can see [ All models] had a rear-window defogger.
I found this and more at The Valiant family site. no pic yet