I use a slightly modified relic mode and TTF most of the time and (I know, I've said this before but) ... use the numbers. If the Fe number is reasonable, pay it no attention if you're getting a consistent peep even of a Co tone. Watch the Co number. If you are hitting a masked target the Co number will jump all around but will regularly hit on or really close to the number of the target (47 or 48 for a quarter for instance) the Fe number does not matter unless it is way off, if it between 8 and 16 (sometimes even more off) ignore it and put all your attention on the Co number... if it keeps flirting with a good number dig it. Heck, dig it anyway unless you are hunting a place full of cut square nails... they will fool most any detector. You can learn to ID most any coin, button, or bullet this way but don't forget that gold can come in anywhere in the Co range and silver dollars can give you odd Fe and Co numbers... a stack of quarters will give weird, way off readings on most detectors. Try swinging over a quarter then add on, two, three, four... you'll be surprised at what happens. When in doubt dig but.. the ET is the BEST machine I have ever used for finding masked targets in "hunted out" places. The Co number will tell you what is there once you learn how it communicates. Particularly on one way hits... that is where it really shines and finds what the others miss.
Julien