I found a wagon wheel outer rim last week. It took me about 1/2 hour to dig out and it was laying maybe an inch under the surface. Why did it take so long to dig, you ask? Well my machine was giving a huge signal (of course) that read like a quarter. I was thinking CACHE!!!! I dug down about 3 feet and found nothing and widened my hole to about 3 feet and still nothing..........widened it some more and realized I was digging right in the center of this big wagon wheel rim that was nearly laying on the surface. I wasn't amused.