More fun facts about OEM paint:
Bigblock261 – Ford and Chrysler were using enamel on their cars in the 1950s. GM was taking a different route by painting the bodies in lacquer and the wheels only in enamel. What I’ve been told is – GM did this for the same reason custom cars were painted in lacquer – you got a nicer shine without the “orange peel” found in enamel. And, as we all know – shiny paint sells cars.
Another consideration on lacquer, GM, and DuPont: If you use the TESS search tool at the US Patent and Trademark Office web site (listed earlier), you’ll note that the trademark “Duco” was first used by DuPont on June 1, 1920, the trademark was filed on November 1, 1923, and officially registered on April 29, 1924. (serial # 71187804 and registration #0183504). The filing that I believe actually covered nitrocellulose lacquer was first used on August 15, 1922, trademark filed on June 7, 1924, and officially registered on October 20, 1925. (serial # 71198225, registration # 0204398)
GM and DuPont worked together to develop nitrocellulose lacquer as a replacement for the hand-brushed varnish used during this time. It took about 3 days to paint a car in varnish, and was a massive bottleneck in production. So, GM and DuPont had a long history of working together on paint. The above trademark dates are consistent with the history as I understand it.
That doesn’t mean that other suppliers weren’t used (PPG/Ditzler or Sherwin-Williams). I can’t prove that one way or another. But, I do know it’s a longstanding maxim to never mix paint brands when painting a car. So, one paint line in a given plant would pretty much need to be supplied by one vendor.