FallisPhoto
Veteran
The brittle ones at least (I haven't ever tried a burn test on a good one) actually were vinyl coated paper.
Sevo
Yes, I know. From what I have seen, they are very like the material used to make shopping bags. The better ones were made of cellulose leatherette on a cloth base (Kodak, Balda, Zeiss, Welta, Voigtlander and etcetera). With minimal care, those can last 50 years or more with no problems. The best were made of leather.