Kinda looks like a gold wedding band got lost down an old iron drain trap or plumbing of some sort and got rusted in there pretty good, or its just water brass that looks like gold but very cool, do an acid test on it?
I cleaned it up a bit and it def looks brand new gold lol… something this old brass would have some tarnishing of some sort..still no idea what it is but the gold continues into the piece but I’d have to destroy it to get inside.The way it is corroded around it, that might just be gold. My thought is part of watch mechanism that was gold. Looking at the shell casings my it for comparison, it's too small to be a wedding ring.
Could be brass, seen similar come from aerobic conditions.
Just to clarify your statement of contentbrass will come out clean in saltwater in some spots
depending on its content - if its mixed with copper - thats when you get green
ive gotten 100s of gold from Ct waters as well as brass items