Apparently in the olden days long before the best before dates were introduced, they used to throw a can of food on the ground to test it, and if it didn't explode it is safe to eat. Did your grandma do this first?
No not that I recall I think we only found out when clearing after the meal but I also remember on another occasion my Grandma had a bottle of cold remedy that everyone had had a spoon of since the 1950s and was still being dished out in the 1970s it was horrible and only stopped being used when the bottle screw top finally gave up the ghost and refused to undo