I happen to have inherited 3 unexpired, prepaid processing mailers for colour 8mm movies.
They date back to the late 60s-70s, and they have no expiration date.
I happen to have one roll of Ektachrome 160 Type A Super8 film, which (to the best of my knowledge) can still be processed correctly (EM-25/26?).
My question: Are these mailers still useful for developing Ektachrome film?
Not even going to ask about the other two rolls of Kodachrome II film in my possession, unexposed.