Yes. those were minted before 1964 and has 90% silver in it.
When you place it on top of your finger tip and bang its edge with another coin, it will ring very beautiful sound for a quit long time. That's the real silver coin!
inflations.us/coins shows dimes are worth $2.12.
each roll has 50 coins in it, so 50 * 42 = 2100
2100 x $2.12 = $4,452
So the coin deal benefited $1,052 if the lady only received $3,400.