Me either woody, especially since it's got such tool marks. They would have had to tool the lip first to place it.
Maybe they had a way to pre-manufacture the lips?
Time to hit the books.
Of the few I have seen, I would call it an inverted blob top. I have never seen one with the closure, so that's not much help. It was NOT an error by the bottle blowers. That's the way it was supposed to be.