My mother at 75 years old (and always complaining of stomach issues) says that the doctor found one of those old fashioned aluminum pop-top lids from a soda can that had been in her stomach for ~50 years. I thought it was odd that she ALWAYS poured sodas out of the can before drinking them and told us to do the same. When I asked if she remembered swallowing the pop-top lid she did remember swallowing "something" when quickly swigging a soda at a picnic in her 20's. I was surprised that the aluminum lasted that long in the stomach (and didn't pass).