certi-card

When i got my 66dart, on the passenger side fender-well there is a little pouch that had a card with the origonal owner name adress ect. I was curios as me and my father (whose been round awhile) had never seen one. How rare are theese? How many people have them? Does anybody recall if this was a standard procedure, special order only, or did everybody get one fron the dealer and are just easy to lose?