I found this on the beach today. There is a quarter for size reference. At first I thought it might be a rivet, but it's made of copper. And the more I look at it, I can't tell if it might even be brass. Dad thought it might be part of a solenoid (picture windings around it) from something. Pictures aren't good (phone, sorry), so I doubt anyone can see; but there is what looks like an iron rod in it with a slight gap between the wall (would suggest solenoid somewhat). I was thinking it might be a terminal post of some sorts. Any ideas? Thanks