It has to be a pool of technicians, specialising in setting up coating machines, optical manufacture etc. Perhaps a machinery manufacturer.
All my books, or rather 98%+, are European, I can't see any reference to Dupont manufactured films or paper other than the Adox brand of films in Germany, which by 1954 were made under license from Dupont by Schleussuer. Certainly no mention of film or paper in the US after WWII
As I said earlier Dupont were specialists in Cellulose & Polymers, did they make film base ? Did they make the base materials for 3M.
3M were not involved in the graphics/photography market until they made acquisitions in the 40's. They made their millions inventing Sellotape & masking tape as well as "wet & dry" sand paper.
There is something going on in Rochester and major changes after WWII.
Ian