It looks like the dime is tarnished. Normal weight for a clad dime is 2.27 grams. Does your scale weigh to 0.1 grams? If so a coin that weighs 2.24 grams (which is within Mint specifications) would show as 2.2 grams on your scale. I would suggest you weigh several other clad dimes and concentrate on the difference in the measured weight between your dime and other clad dimes rather than the weight your scale displays. (Your scale may not be super accurate with the absolute weight.)
Looks like it's been in the ground, may be a MD find. I have found may that have been lost in all different places and the coins all have different colors. -O)
Not an error but I've got to admit I like the way the reverse looks. I would probably keep it if the obverse wasn't so spotty.
