Is the patent Usd471730 valid? This is the polyprop chair but the patent is quite recent, much more so than the chair's invention in 1963. I am puzzled.
This is a design patent. Unlike utility patents (what you normally think of as a patent) design patents are not related to functionality but just to the esthetic design. As you can see, the examiner looked at a few dozen similar looking chairs, including the 1963 Polyprop chair. Whatever differentiates the this design from the Polyprop, Eames, Alvar Alalto, etc. designs is what is covered. If the differences are small, then the breadth of coverage is also small.