This is a retainer used only on 1965 Mustang Fastbacks folding seats, Ford service number - C5ZZ-63130A18-B. In 1965 only, Ford used a rubber bumper 1 inch in diameter, 5/16 inch thick, on the curved section (11564 in the drawing below) to cushion the section when folded back to make a seat. It is not reproduced, and is not included in any reproduction "Molding Sets". I had this piece rechromed about 10 years ago. Note the tabs on either end and the absence of a 5/16 clearance hole for the larger bumper.
$150.00 plus $15.00 shipping USPS, USA only.
PM me for more details.
Jim
