I just read a terrific post titled, Shooting and Developing a 70+ Year Old Roll of Kodak Plus-X, where a photographer bought rolls of Kodak Plus-X film at a garage sale, loaded one in his camera, took pictures, then processed it.
One of the gems in this post is: "Exposing film [this old] was a bit of a gamble. The rule is to overexpose by 1 stop for each expired decade, but 7 stops below ISO 100 or 125, the nominal rating for this film, would be ISO 0.8."
I think working with expired film is one of the most exciting aspects of analog photography. And even though I've never found rolls that are 7 decades old, I can appreciate the adventure that photographer Tony Klimas embarked upon. And the shots he produced are terrific.
I highly recommend reading the article. (Original post and photos by Tony Kilmas on PetaPixel)