I can't tell from the pictures if it's round like a ball. If it is, it looks to me like an attempt to cast a lead musket ball. If so, the reason it turned out that way is possibly the mold was cold and he didn't get a good pour, or it was the last of the lead and there wasn't enough to finish. I've cast lead bullets, and both of those have happened to me, along with getting my arm bumped, but usually it's from a cold mold that casts a poor bullet, so usually several are cast and tossed back into the lead pot to remelt until the mold is hot and casting proper balls. If not completely round, then perhaps fishing sinker looking like that for exactly the same reasons above. All that's just a guess looking at a photo though.