Chipper fragments would make about as good sense as anything else. These are not hits from anything like wire or buried pipe, nor from nearby metal like the supports for the swings. All the hits are small and random and not just directly under the playground equipment as you would expect. It could be that my dying batteries in the detector had something to do with faulty ground balancing, too, as they suddenly went dead after about an hour of detecting. There are several separate areas where wood chips have been put down under swings, jungle gyms, a carousel, etc., all places which would be excellent candidates for coins and objects falling out of pockets, but so far I haven't found even rusty little brads, which as you know are almost impossible to see even when you have them in your hand with a handful of dirt. I now have a fresh set of batteries and will try again, weather permitting, and will tune both the air and ground settings more carefully. This Whites (sorry, it's at home and I'm fooling around at work, so I don't have the model number handy) has a somewhat perfunctory discriminatory setting, so I'll fool with it too with some test coins and slugs at home and see what happens. I still think that I should be able to come home with a bucket of coins from a school playground that doesn't seem to have been hunted, assuming that someone who had hunted before me would have disposed of the 2-inch-square piece of iron and 12-penny nails that I dug up from the site!