Scott, I think you have conductivity and composition mixed up. The detectors that are made for gold (nuggets) simply excell in getting the lower conductivity little stuff, amidst mineralized areas. They don't specifically get "only gold". In fact, they are quite hot on nails, bullet shells, and other stuff found in old mine tailings. Coin machines are better on disc'ing out trash, and getting deeper on coins while doing so. Both machines use conductivity to decide what to disc. out (assuming your gold machine even has a disc. circuit). SO, when your coin machine reads something in the "gold" range, it could also (most likely) be a chopped pull tab, wadded foil, etc.... If they ever make a machine that tell composition rather than conductivity, people would sell all they had to own one. All you can do for now is maybe buck your odds a little, but for the average junky park, that still means aprons full of trash for each gold ring.