How to tell a real GM window sticker from the repo

[Jeff H]

I have a couple of blank GM window stickers that a guy sent me. Is there a way to tell the real GM window sticker sheets from the reproduction stuff you see at the shows? They sure smell old and musty like they've been sitting for a long time. I figured they might be good for comparing possible fakes. I have no plans on using them to dummy up a window sticker for my car. He also sent me an old Baldwin catalog/order form which is pretty cool.
Jeff H.