Kevin just a suggestion that some not all will agree with. If you drop your volume gain to about 26 the deep nails will not sound as good yet the deep coins will still come through good and will sound deeper than the shallow targets, also set your threshold tone to 1 with your limits to 30 this will give you the widest variation of tones. With this set-up I can tell the difference most times in silver dimes and silver quarters from clad dimes and clad quarters by tone alone. You'll be able to tell the difference in a deep nail and a deep coin.