It's hard to say when it was done. If you do a punch that close to a bend line, it would distort the radius when forming. It looks like that is happening, as the corner at the bottom next to the radius is shaped differently from the opposite side. If you machine after the fact, it would probably give a more uniform on the end of the slot.
Keep in mind that a lid with slots like that would allow cool air to bypass the vacuum dashpots that close when cranking the engine cold, so it would possibly negate some of the emissions hardware.
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