My deepest buckle was about 12" but it was flat at the bottom of the whole, it was a big ish spectacle buckle,my deepest coin was an old pre decimal penny at about 10", my deepest bit of plough was 2 foot, I have dug deep wholes but the target either fell in as I dug or it was in the sidewall, and to be honest who wants to be digging a 2 foot whole to find a bloody old pre decimal penny or a poxy drinks can ! I know I don't, not on a day like today that's for sure, far too hot outside to be digging that deep in this heat !