Im not certain you would know that unless you received an occassional bleep, VDI or signagraph that made you dig. However, with +95 on i have noticed when you get below say 7" you may get wrap around from coins that read in the low iron from wrap around. You have to kind of pinpoint and test to see if you are dealing with a target the size of a coin and dig. You may get a DC phase on the coin. You may also get positive readings from larger pieces of iron just on the edge of you coil, but i can normally tell if its big or coin size. my 2 cents worth.