Well, I've never worked on one of these. But I'll tell you about the number plate on my vintage Cadillac: what I thought were rivets were actually little brass nails. If you knock it down, and look at the inside of the fan case, you'll be able to tell if they're rivets or nails. If they're nails, just pound them out from the back, if rivets, you'll have to carefully drill or grind them out from the outside.