If you look at how they word the listings, they usually try to use non-definitive wording about the age. It'll say "old" or "vintage", something like that, something non-descript. Also, how many people would bother go to court saying the item was misrepresented as original? and not always easy to prove its not original.
As far as copyright infringement, depends on how hard the company defends it. For example, Harley-Davidson is aggressive and you see one-off fakes but not a lot of unauthorized reproductions. Coca-Cola does that too, they are real aggressive, too aggressive. I've heard Sinclair and a few others defend well. Keep in mind that these companies do authorize reproductions. If you are a real company using someone else's copyright, the fines can be really severe, usually based on each occurrence of unauthorized use. Lot of the older brands that are no longer in use are free to use without issue really.
