Join us on Facebook: Search for 'ConcoursMustang' Private group!https://www.facebook.com/groups/concoursmustang/Indiana SAAC Fall Classic , French Lick, IN Oct 11-12http://www.insaac.org/SAAC National-Sanctioned Concours Event
Never have seen that on a car - maybe like you say it is something that appeared on service parts? Fortunately DNO is reproducing them with the Fomoco stamp: https://www.deadnutson.com/1969-73-disc-brake-driver-side-dust-shield/