Tom, I was using a Metrotec. They where basically converted gas & water line locators. Worked pretty well for their day. As for that first find it was right on the surface, an inch at most. I had just got the machine. Took it to the backyard. Tuned it. First sweep "BEEEP" there it was. Dont recall depths from back then. I do remember going quit deep for a silver dollar in some sandy soil, maybe 7". But everywhere I went back then was pretty much virgin ground.