Could anybody identify what's gone wrong here please? I inherited this from someone, didn't really know what it was supposed to be like, sold it on, and now the guy's complaining that its broken... well, obviously it's not BROKEN as such, but I suppose I see what he means - the top case doesnt look like other ones I've since seen - it has these funny slits in it! Anybody know why? Is it from a different model? Can I just replace it with the correct top case? Thanks!