A number of years, ago, my friend and I detected a plowed field that was a fairground which closed in 1910.  We had hunted about two hours, without any luck,  and, while I was walking to my van, swinging my detector in front of me, I got a loud signal from a dirt clod.  I picked up the clod, broke it open, and there was this nice 1875s 20 cent piece.