The reason I asked about discrimination settings is because I've hunted sites that were home to old blacksmith shops, and they are typically littered with iron. That iron will rust over the years, making some spots a difficult situation to hunt, to say the least. If you are running with the iron discriminated out, it is highly possible that the threshold is nulling over those patches of iron (and iron oxide) and you're not hearing it. To see if that is happening in your site, grid off a spot about ten feet square, and hunt it in Prospecting mode. Mark any targets you encounter with a golf tee or something that is non-metallic. Then go back over that same area using the set up that you have been using. See if ALL the targets you found in Prospecting are providing the audio response you expect in Coin/Treasure mode. If you have zero discrimination, you should hear them all. If you are using some discrimination for highly ferrous targets, you should hear a nulling of the threshold, indicating that the X-TERRA is discriminating them out. Do it again using a bit higher Threshold. Raising the Threshold another click might allow you to interpret any nulling that you are currently missing.
If you are wanting to pull coins out from between those masses of iron scrap and iron oxide, you may want to run with zero discrimination. And to really sort through the iron trash, use a small DD coil, overlap your swaths by half or more and work the area from different directions. You could still get some masking from the iron. But using the small DD, overlapping your swaths and working from different directions will give you the best odds of separating the targets. JMHO HH Randy