Mark,
I checked the doors on my current car as well as photos from my last car, both Dearborn built, and each door had just one stamping. I also dropped by my local classic car parts yard and of the 43 '65 and '66 doors they had; 30 Dearborn, 9 San Jose and 4 Metuchen, none had more than one stamping. Disappointing, I was hoping to find at least some or one with a double stamp, but no luck. I also asked someone I met recently, whose Uncle worked as a foreman on the assembly line in Dearborn and still owns his original unrestored very early built '65 Coupe and he has no recall of why there would have been a second stamping.
No help I'm afraid but it was interesting and a treat to talk to someone who was actually there.
Ray