PSD. Not a good thing. In the 1960's they used to take a cent to the chemistry lab, dip it in acid and reduce the size of the cent. Then they would put it into a pop machine at that time you could get a 7 oz soda for 7 cents and a 10 oz soda for a dime. Because if thinned and reduced the width, the machine thought it was a dime. If you put an acid treated cent in the 7 cent machine, then you would get back
Three Cents in change and a soda. I never did that though. I never thought of that. but it did happen.