StoneNYC recently got a stash of films dating as late as 1947 with no edge markings.
I advised him to be careful as it might be the Nitrate based. He gave it a "safe" ignition test and it went up in a flash. So I'm looking at some information that says roll films used it even in the 40s.
This comes from a PM, but since it is critical to know for safety, I thought I would bring it up.