I just picked up a few old tins of tobacco(Rattray's black mallory, 7 reserve medium, red rapparee, sam gawith's westmorland mixture and navy flake. All the cans hissed indicating a vacuume seal. The paper inside the tins however were brown and seemed to have absorbed a bunch of moisture from the tobacco and i noticed little white specks on the flake. I just want to know if these are okay to smoke and is there a shelf life to the tins that should concern me. and how would i know if mold had gotten into the tobacco (although i dont see how that is possible as the tins did hiss when opened?)