Something to think about:
The coin acceptors in vending machines are highly sophisticated metal detector type instruments. They can tell the difference between Penny's, nickels, dimes, and quarters. And, if you put in a foreign coin or a slug, they'll know that too.
But, If you put an American dime into a vending machine, it doesn't matter if the American dime you put in the vending machine was a silver dime or a clad dime. The coin acceptor in the vending machine will still see the dime as an American dime, accept it, and give you your can of soda.
In addition, it doesn't matter if the American dime you put in the vending machine was a Roosevelt Dime, a Mercury Dime, or a Barber Dime. The coin acceptor will still see the dime as an American dime, accept it, and give you your can of soda..
Where am I going with this?
To keep the correct change from being rejected by vending machines, the U.S. mint makes ALL of it's clad coins to look IDENTICAL to a vending machine coin acceptor as the silver coins that preceded them.
If a vending machine coin acceptor can tell the difference between copper pennys and silver dimes (something our metal detectors have a hard time doing), but, can't tell the difference between a silver dime and a clad dime, it's pretty tough for us to tell the difference with our machines.
My personal opinion is that when people say they can tell the difference between silver dimes and clad dimes, it's a myth.
Maybe they can but, it's very doubtful that they can do it 100 percent of the time.