Joel, while it is true that small to mid-size gold falls into the aluminum range, I don't think you have answered his question. There might, in fact, be locations, where someone isn't going to be a hero, and may just go for coins (deep silver, etc...). There are turf environments where I and others (gasp) pass surface tabs and foil. There are simply some environments where .... to dig 200 pieces of can slaw and tab slaw, is just not an option. If gold jewelry is a person's goal, then they'd be better served by just going to places where gold jewelry has a better ratio. Namely, swimming beaches, or turf next to swimming pools, etc....
So to answer throw-down's question: There is no reason why the Advantage's disc. control can't be advanced enough clockwise, to ultimately knock out aluminum (foil, then round tabs, then square tabs, etc....) while still keeping pennies, dimes, quarters IN. Something is wrong with the way you are detecting, or something is wrong with your disc. control, or you must have a type "pop top" or pulltab that is large enough to come into the penny/dime range. Can you post a pix of the type debri you say can not be knocked out, even at the highest settings? I have used the Advantage, with success, in pulltab riddled zones before without a problem. Was able to knock out low to mid-level conductors, and effortlessly pick out wheaties and such.
Try round tabs in an air test, while slowly advancing the disc. control. You will see the point on the dial where they start to "break up".