I found a super sensitive metal detector in a flea market. It's a Fisher Model 65 M-Scope made is Los Banos, California. It says its a "Valve and Box Locator". It worked fine for finding my son's class ring lost for 10 years in our woods.
I took the detector out in the woods to see what I could find when I first got it. The woods in the front part of our property are a second growth stand of tulip poplar, dogwood, and spice bush. That part of the property must have been a hilltop meadow a century or more ago, based on the items I found. The items were: a clothes hook (part); a non-ferrous butter knife, a fish hook, part of an iron ring, an iron tent peg, and a cast off hand-forged horseshoe. The area these items were found in was about half an acre in size.