Your trunk lid is not for a Demon. It is a 70 and up Dart Swinger/Plymouth Scamp trunk lid. I believe it will fit Darts and Scamps from 70 up until 73 and possibly 74-76 as well.
As far as value is concerned, they are very common and I am pretty sure the 4 door lids are the same as the 2 doors so they are not rare and yours has rust so I would say $50-$75.00 would be a good price.
Joe
