As Bill said, the old compass 77b will do it as will most 100 khz TR's but having tested many detectors with a coin 2 to 3 inches down under one nail I don't think there's a vlf that can do it. The only detector I've used, and still use for trashy sites, that can consistently hit a coin 3 inches down under one nail with disc set to just reject nails is the old, 1990 model,15 khz Gold Mountain GMT 1650 and it will only do it swinging across the nail. And forget about telling it's a coin of any denomination, the best you can get is an average of the two conductance ranges. Let me add that we have virtually 0 mineralization, throw some bad ground into the mix and results go from bad to worse. As for the depth of the Compass TR's, they have pretty good depth in low mineralization. In our ground they can do 5-6 inches and maybe a tad deeper on larger coins. They are great for hunting where the ground is full of nails, I keep one around and use it fairly often. True, they have no discrimination but after using one for awhile it's easy to tell larger trash and coins, buttons and similar size nonferrous targets give a fast on/off "round" sound so not as much junk is dug as would be expected. The link below is a post I made last year and has a comparison of 3 detectors. About halfway down is the test using a dime and nail, the results were better than any of the other many vlf detectors I've done the same test on.
JB
