I don't understand some of the 3d's are not the same when air testing, You don't find coins in the air but air testing should be the same. I have had my 3d for over a year and I checked the one I have with over 50 nicks new and old buffs, liberty.In both modes disc 0 all nicks read nick high tone, 8in coil or 5in coil.??????????HH BILL-NC.