Of course because of technology the machines today are more sophisticated. But in the old mechanical machines, if a coin was the same size and weight as a dime, it was accepted as a dime. Many times it was just the size of the coin, and as long as it fit the inner dime slot, it would register as a dime. Dime sized slugs were used besides ground down pennies which take a lot of work for the crime of stealing 9 cents. Parking meters and pay phones took dimes, and they were targeted in this manner. Pop machines way back when, a soda cost a dime.
