My brother gave me a Radio Shack Discovery Three to throw out or to put on Ebay.His wife bought this detector a few years ago as a gift and paid a lot of money for this detector.(Radio Shack)He said it was absolute junk and never could get to work right, or find any thing with it, and now it didn't work at all. With cabin fever I took it apart and found a lose wire on the toggle switch tuner.I soldered the wire back on and ran a few air test with coins.I ran a quarter, dime, penny and nickle past the coil and it ID'ed every coin. OK here's the sad part, I got an air test of 12inches on a quarter.The detector looks like a Teknetics Mark 1 with a different ID system. Has anybody ever used one of these detectors and how do they perform. Ron