So, I finally tested all the old Dupont paper I'd accumulated. A lot of grade 1 & 2 Apex (a contact paper), Warmtone DS, and Velour in grades 1-3. Not a lot happened in base fog tests. But after a lot of years those paper envelopes crack..pitch black within a couple second of going into developer. I was really pissed- paper after paper turning black. I'd saved the best for last, some Grade 3 Velour in a T surface. I still don't know exactly what this surface is. Exposed some random shot on it and printed perfectly, with very very minimal base fog. Expired 1953. I'd like to generalize that these papers can still be printed on provided they're unexposed. They have quite a shelf life. I'll be starting anti-fog tests in Dektol to bring it back to white.