I and my hunt buddies made a test plot to check our equipment on, it has silver quarters and dimes, clad, nails, brass, horseshoes and wheat pennies. In preparing for an up coming hunt we were testing our machines out in the test plot and my two hunt buddies equipment was working well, but my machine did not pick up on any of the targets but my partners did. I checked all connections and put new batteries in and did a factory reset twice but it still would not zero in on any of the targets. These targets have been in the ground some three (3) to four (4) years now. The test plot was grid and mapped out with each targets location, depth and target ID. I'm using one of my back up machines for now.