Avoid the temptation to muzzle your F-75 too severely. At first I was running a discrimination mask of 55 with nickels notched in and I might get to 34 or 35 on the sensitivity in default or bottlecap mode. Now I run discrimination at 15 and no notch. The sensitivity can be run up to 85 or 90! More signals, but dig only the steady TID numbers when swept from different directions. If it hops 5, 10 or even 20 units, it's trash. If it only varies one or two, or none, it's a coin.
The caveat is that you have to somewhat memorize the trash and coin ranges, and there is a danger a signal outside the common coin numbers might be an uncommon coin or jewelry. The F-75 display has bars for Nickel, Dime and Quarter+, but they're wide ranges. You can be much more specific (i.e dimes are 70 or 71 in my soil).
When in doubt - dig.