I think it has to be lead because it’s so heavy, I don’t have a great metal detector but I do know it isn’t iron.What metal is it made of? Looks like a lead plug.
I am admittedly a beginner when it comes to this, but it just doesn’t look like it was machined, it’s just way too imperfect as far as the shape goes unless it was severely warped when it was broken off of whatever it was( if it was even broken off)I see splines too, and a screw hole. makes me think faucet stem .![]()
or a lead anchor![]()