I think it's a counter weight for something, big window, a gate, barn door I found two big lead weights like that, but the had a cylinder shape. Definitely worth its weight in lead.
Hey, it was fun running into you guys at that cellar hole. It's looks like maybe a slave ankle chain and ball. Like this because of the shape. Forged iron slave shackle with ball and chain, definitely 19th century, from a Civil War collectio I thunk you found evidence of the underground rail road in this area. Unless it wad s counterweight for something. Never sen window weights this shape so it would have been from something else I think. That is if it's not a ball from as ankle chain.
I would have to say counterweight for something like a coop door or animal hatch/door..It's to crude and odd shaped to be cast for a slave ankle chain..Plus if it was a lead ankle weight it could be easily melted away for escape..But it is a cool find!