I am trying to find a delicate lady's platinum ring set with a 2.5 carat diamond lost at a wedding. The top soil is a layer of varying thickness of heavily-trampled hard pack with enough iron to plate sandwich coins so dimes and quarters in it even long enough to be driven two inches down read a FE of 13-14. The subsoil has numerous nails and wires, both new and old, left over from years of outdoor theater that give a reading of FE 35 - CO 48. The ring was lost four weeks ago and should not be deep yet (I hope.) So far I've been digging everything with a FE or 10 or less at a depth of five inches or less regardless of CO and found a couple of small sterling rings, but I've still got a lot of ground to cover looking for the platinum one. I would deeply appreciate any advice on settings and what numbers I should be looking for. Thanks.