The secret to this thing lies in the swamp...A few years ago with the deep max they hyped up the "big" gold hit...And after sending Duffy out there flopping around in the mud looking for it ...Nothing, phony target, "that's Oak island" whatever...Well, that machine is not only expensive, but quite accurate, And quite surprised Calico (and there plant Gary) sat still for the apparent failure of their flagship....My guess it was picking up gold ions in stagnant water that dissipated after stirring it up...Somewhere close is/was a big pile of non ferrous metal.