its easy -- just run the desired item under the coil look at the number it gives you -- I use a delta 4000 a lot -- I honestly feel that its 0 to 99 numbers sorting display is much more accurate than the ace 250 by far --yes the ace 250 can and will find gold ---found a paper thin 10 k kiddie ring (made in Mexico type) that rang up as "foil" as a by product while digging up a -coin spill at a local baseball diamond that the kids youth league plays at --with a ace 250 ...the numbers you really want to be on the look out for are 58 --10 karat -- 64 that's 14 karat and 68 that's 18 karat -- 77 is zinc cents and indain head cents -- 82 is older pre 1983 or earlier copper cents and clad dimes and silver dimes --mid 80's is quarters --high 80-'s is halves ---60 is often a aluminum pull tab --- since natural unrefined gold can vary in its gold content any thing from 58 to 68 you should check out --for sure the "numbers' are where the item hits on the machines "electrical coinductivity " scale with 0 being low and 99 being high-- iron is at the low end with the next being aluminum , then gold then zinc cents the copper , clad coins then at the high end is silver ...as one notches out or "discrimates" one drops out of detection various metal going from low to high --the higher the disc the less metal you find ... one wants to cut out as much aluminum while retaining as much of the gold as possible when ring hunting ...natural gold nugget hunting is a bit different since gold nuggets --gold content can vary due to their make up and various impurities in them