oklahomahunter, I'm having trouble understanding what you're saying here. Are you saying that on a particular disc. setting that the PULLTAB still gives a "strong signal", or that the SILVER DIME still gives a "strong signal" ?
Just do this: take a square tab (preferably the beefier/thicker type) for an air test: slowly advance the disc. control until that square tab is eliminated (but no further !). Or another item to use as this benchmark, is a corroded zinc penny (or a non-corroded one, if you also want to pass on zinc pennies totally as well).
There's lots of places that I too elect to pass aluminum junk, and just go for the coins. Like underneath bleachers, where it's an ocean of aluminum. I just shoot for the coins (and silver coins). Because you're right: in those environments, it doesn't pay to "be a hero" and try for gold and nickels. If someone's that dead-set on finding gold, then what-the-heck are they hunting underneath junky bleachers, or blighted parks, to begin with? If you want gold that bad, simply go to a swimming beach, NOT under bleachers, haha