Here's the nut now that I took it off. Those slots closed up about .005" after I took it off, so it's some kind of lock nut although I still don't see how it works. Maybe they bent those wings slightly after they cut the slot to make it bind up on the thread. It was so hard to get off I used a 6' cheater bar, I thought sure the threads were galled. I can't imagine a more expensive way to make a lock nut.
