I keep seeing TV ads for metal detectors. You can detect coins! Jewelery!
If I'm going to a site with potentially buried monitoring wells or other useful infrastructure, I take along a metal detector. I never find anything interesting - I'm lucky to find what I'm actually looking for.
But that's because we wouldn't expect to find anything terribly interesting in the back of an old industrial park or factory, right? What if we go to a more interesting location?
I once had to remove all metallic debris from a historic military site - prime pickings, right? So what did I find?
1. Several horseshoes.
2. About 20 old bottles with screw caps.
3. A couple of bucks' worth of modern loose change (mostly nickels and pennies)
4. More than fifty feet of barbed wire, all snarled around itself 2 feet below ground surface.
5. Approximately 10,000 rusty nails, washers, paperclips, brads, and staples.
6. Lots and lots of indeterminate scrap.
7. A surprisingly large number of iron-rich rocks (unexpected for the local geology).
8. A bunch of bottle caps.
And then I found something explodey and I didn't get to pick nails out of the ground anymore.
Anywhoo, the point is that after poring through this fertile ground for almost a week, I had found little of interest and zilch of monetary value. So no, I will not be purchasing my own top-of-the-line metal detector to explore the detritus around my yard.