I dig a couple inches short of the target only to avoid scratching, slicing, gouging, denting, or otherwise mutilating what are sometimes 200+ year old coins around here. Before I got the X1 probe I routinely ruined them, now I don't.
But lets talk about the false signals, the dreaded rusty nail lying flat tossing a signal off sideways towards where you thought a coin was. You dig down, nothing, a littl deeper, nothing, check the side of the plug and find the nail sticking out.
Or even better, the combo rusty nail/coin in the same plug. This is where the tone ID is king, left side of the hole...rusty nail...right side whopping silver hit.
Or the common silver hiding underneath a rusty bottlecap, out comes the cap, back in with the probe and whammo silver.
Or the ultra-deep large cent which reads more shallow than it really is on the meter. It says 8, you go down 8 nothing...carefully take out another few inches, now you can hear it.
Here's a story for you, I took Carl (a local dealer) out to a spot I was hunting, he got this great silver hit, strong, and he dug and dug and dug, man he was down a good foot and nothing but it was still sounding off solid. He didn't have a probe for his Explorer at the time but I did. I came over and located the coin scanning through this big field stone (huge flat rock). The stone was too large to remove so he dug out underneath it, reached in and yanked out a ...drum roll...1800's silver DOLLAR!