Someone may have tried to simulate a dime struck on copper plancher or represent a dime without the nickel layer which would show the copper core. Easiest way to do this would be to cook the dime in boiling salt water and they leave it out to dry in the sun. It can also happen without human tampering if the coin was submerged in salt water from say a pool, fountain or in the ocean for quite a while. It could be a beach find that made it's way into your pocket change.
Yes. I find dimes that look just like that with my metal detector all the time. They retain their detail from the day they were dropped but discolor, in most cases.
