[Calvin Locke]

I bought one years ago, in my teens. Lots of AA batteries, as I
recall. Had a very loud find in the yard, dug down,
downwards of a foot, and found a piece of aluminum
flashing...

My brother lost an aluminum shaft arrow in a field, and I was able
to find it. Headphones are very helpful, btw.

Did you know the first attempt at a "metal detector", although he
called it something like "resonance oscillator", was by
Alexander Graham Bell in trying to find the bullet in President
Garfield?

It was a failure.

For me, I found contemporary coins, fastener hardware, and the
like. I guess it was a form of recreational exercise, when all
was said and done.

[DBrow]

“My brother lost an aluminum shaft arrow in a field, and I was able
to find it.”

High-end carbon fiber target arrows have a metal wire so you can find them with a VLF detector. At $20 each, if they fall to Earth you know not where, a $200 metal detector is a reasonable investment.