You might want to reconsider throwing that casino chip into the wishing well, there probably wasn't a magical fairy after all. According to Wikipedia it might have started out as a game or even an early form of gambling or wagering, a game where the coin wasn't even the prize perhaps?
"another local custom at Askham is the throwing of coins from the nearby bridge onto a boulder that lies just below the water level of the river. Getting the coin to land on the rock gives the thrower "good luck." Obvious connections exist with water generally and the practice of throwing in coins to seek favors of the water spirits ".