I'm late to this, but I figured OP might enjoy this story... I did some metal detecting in Colorado when I was 14. Found a huge signal, and so I was banging on it with a metal shovel trying to figure out what it was. And then things happened.
I was camping in the mountains near Colorado Springs and attending a weekend starparty with my Uncle and his family. He built telescopes for a living, and Hale-Bopp was doin' it's thing. The astronomy part of it was cool enough, getting to use a healthy mix of custom-built and some high-end telescopes to watch the comet, and to watch other things up in the night sky. My Uncle and his coworker brought a proprietary giant binocular setup that I had to climb a ladder to look down into... and behind me, it was pointed at Jupiter. I could watch the moons glide past the surface of the planet, shadows cast down below. It was a zen moment.
But during the day... it was boring. My uncle's friend handed me a metal detector and a shovel and told me to go find some stuff, I'm guessing to get me out of their hair.
I found some spent rifle shells, some comm wire, some twisted metal hangars I'm guessing was for smore making, etc.
Well... late in the afternoon on Saturday, I found a large "bloooop" and started to dig. I couldn't place what it was, but I dug the hell out of it. Banged on it. It was solid, I thought it might've been some sort of foundation for a pole, kind of like what one might use to sink a tetherball pole into the ground. I dunno, that's what my kid mind thought.
So I dug a moat around it. Was about 12" to 14" in diameter. The clang the shovel made as I banged on it made me realize it was solid metal. Round. Still couldn't place what it might be. Treasure though, right? Maybe it was treasure.
I keep banging... and realize it's got more form to it. It looked like it was painted, maybe a blue color and definitely rusted over. There was an inner ring kind of raised a lil', maybe 5" in diameter so I brushed the dirt off of it and it said, "ARMED - ARMED - ARMED" going around the center ring.
And I nearly shat myself. I was banging on a goddamn landmine with a shovel.
I sprinted back to the camp, found the guy in charge of it all... an older guy with white hair, and breathlessly tried to tell him what I found. He calmed me down and followed me out to where I was, then told me to keep back. He walked over to it... looked at it and said, "Yep. A mine. WWII era."
They called the nearby Army base who sent out their bomb squad and bomb robot. They let me try on the bomb suit, took my picture, put me in the paper... then told me it was a dud, used for training. That sometimes they get missed. But to not worry because it was a vehicle mine, and I'd have to drive a vehicle over it so banging on it wasn't an issue.
So... yay?
Got my heart goin' though. I was sad they wouldn't let me keep it though. They had to take it back to the base to account for it.