Ive been hitting sanded volley ball courtsbut neve more then a quarter or so. Horseshoe pits?
One theory that has worked for me is starting with the edges of the site. I'm not quite sure why, but most of my finds (and pretty much all of my good finds) were found at the very edges. I'm not sure why jewelry is so much more common at the borders of public spaces, but that's normally where I find it.
Someone once told me about a girl at work that had an argument with her boyfriend. As she left the parking lot that day and turned onto the main road, she tossed her engagement ring out the window of her car - onto the shoulder of the road.One guy long ago was driving around and drinking. He threw his beer bottle out the car window, and his class ring went with it.
Now way under a highway project.