My first “guess” would be Parrish/Dana in Reading PA as they manufactured auto and truck frames.
The Reading did serve Mack Trucks in Allentown but I don’t recall ever seeing any truck frame cars. I have seen R model Mack cabs on flat cars but that’s beyond the era of this list.
I’ve been digging to see if at this time the Budd company would have been making auto or truck frames at their Hunting Park factory in north Philly but so far nada
