“Detectorist”
Interesting.
There seems to be no other word that describes what we do. I don’t like this word either, but, “I’m a metal detector-er”, doesn’t quite fit, so I’m good with this usage for now.
As not so patiently explained in the first episode of ‘The Detectorists’ (first two seasons available on Amazon Prime—worth checking out) the machine is a metal detector, the operator is a ‘detectorist’.