Coworker found it sitting on a rock while he was walking around picking up trash, very possible one of the landscapers hit one of the "ornamental" rocks around the driveway. Just seemed too big to be a mower blade, but I do agree it looks like it snapped at a bolt hole. Also: it's nice to meet you frosty and Thomas, I always look forward to your responses in threads and you've unknowingly helped me a lot in my short time (about 9 months) forging.