How to tell if it is an original bonnet

Hi - I'm currently restoring a 1981 mk1 Golf GTI 1.6. I've recently bought what I believe to be a geuine bonnet in good condition as I don't want to use pattern. Are there are any tell-tail signs for its originality? I can't find any VW marks on it, but it came with a german high voltage sticker on its underside. The only difference I can tell is the rubber grommets at the front screw in, so are adjustable, whereas they push in and can't be removed on the pattern version. Any ideas?