"... maker of severe-duty trucks. In
1953, Autocar was taken over by the White Motor Company, which made Autocar their top-of-the-line brand."
"... was taken over in turn by Volvo Trucks in
1981 ..."
https://en.wikipedia.org//wiki/Autocar_Company
Not much help, but knowing which years (53-81) it might've been used could narrow things down a little??