I think most of us have encountered areas such as you describe at some time or another. I have a similar site..... 100-year old school that was burned down in the 60's. Nothing there now but nails, scraps of roofing, nails, parts of desks, nails, pieces of copper wiring, nails etc. Oh, and did I mention nails? These types of sites are nasty. But on the other hand, if you have "competition" with other detectorists in your neck of the woods, it is likely that they have given up as well. Point being, there may still be coins out there amongst the trash. For these types of sites, I chose the smallest DD coil available. Personally, I'd prefer a 6-inch DD coil at 3 kHz for the reasons I've stated many times. But since we don't have one available in that frequency, the 6-inch DD at 18.75 will have to do. I don't see a lot of difference in the detection depth between the 7.5 kHz concentric and the comparible sized DD at 18.75 kHz. But there is a dramatic difference in their ability to separate targets. If you don't have the small DD, and don't intend to get one, there are a few other things that may help in this situation. Lowering the sensitivity, slowing the sweep speed, raising the coil and running all metal / multiple tones. Sensitivity, speed and height are pretty well self explanatory. As for tones.....I believe the detector will respond quicker between targets in all metal in that it doesn't blank out over rejected targets as it does when they are notched out. Hearing all the tones can be a bit overwhelming. But the key word is that you hear ALL the tones. Target masking is the culprit here. And anything you can do to reduce that masking effect will help you sort out the treasure from the trash. It ain't going to be a walk in the park. But as I mentioned earlier, if it were easy, someone would have already done it! JMHO HH Randy