I just bought this for a few buck on eBay. How about this crazy contraption for running dunes? The postcard is a jumbo 6.5″ x 9″. I looked for more information about it, but all I could find was a reference in a book by J. Conrad and Kathyln Dunagan about a Jeep developed in the sand dunes (see bottom pic).
“Jumbo Antique Postcard 1970’s Chrome Famous Sand Hills Jeep Texas Sand Dunes”
Google result that shows a reference to a “jeep ride”