Hard to make a guess without knowing what metal it's made from or how old it is but it certainly looks worthy of proper testing and expert analysis
to find out more about its origin.
It could have been part of a larger object and became detached somehow?
That is my guess at any rate but an interesting find never the less so thanks for sharing.
It's probably a joke being played on him by one of his buddies from the "lodge" who's tired of hearing his UFO theories. If he is a serious metal
detectorist he would grid out any area he intends to work making it easy to plant something foreign to make his wheels spin.
just reading some of the replys on the site provided, a few people said it was the dreaded "prince albert" peircing... tsk tsk tsk why someone would
do that to themselves.