A vendor was sorting a vending machine's change when he came across some strange looking dimes that looked like silver pennies. Mysteries of Science
A soda machine vendor was sorting the vending machines change when he came across some strange looking dimes. Upon closer examination he found that they were not dimes at all, they looked like silver pennies the size of dimes.
Under a magnifying glass the vendor confirmed that they were indeed thin pennies that had been coated with silver. These mysterious pennies continued to appear in the vending machine.
Realizing that the penny thinning process could be chemical or mechanical, but the coating was certainly chemical, he sought out the help of a chemist friend to take a look at the pennies. How were these pennies being converted into look alike dimes?
Here is the rest of the story.
Some students were behind the crime. They placed pennies in dilute nitric acid until the pennies were reduced to dime size.
After rinsing they placed the re-sized pennies in a silver nitrate solution. This converted pennies to the size of a dime and allowed them to trigger the mechanism inside the coke machine.