Dave -you are correct. One nice thing about working on such a well preserved and original car is the ability to learn and share with everyone. I confirmed our findings with Mr. Mike Masich. Mike worked in Chrysler stamping during the late 60s and early 70s. He described after stamping a door skin (or quarter panel) they would spray prime and then apply "dumb-dumb" (mastic sound deadener)on the inside, then final assemble the door shell and ship to the assembly plant or parts depot. With this car being so clean you can easily see all of the stages including the overspray in the doors of the assembly plant paints... both blue (interior color) and black (exterior color) are evident and even allow you to vision the strokes of the painter. Hope this helps - Dave S.