I know there are huge numbers of detectorists working over those old parks in Omaha with some very expensive detectors. They have a permit system there last I knew. You give them a little fee & fill out a form, & they give you an ID card with Treasure Hunters Code of Ethics on back, plus a map of Omaha showing every park. Are you signed up for that yet? You just might see a few of them in action. Best wishes & HH, George (MN)