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I designed and sold commercially, in 1987, a rotating Kite. Two Americans, one of them Chinese, got a Patent granted, in 2001 (I did not have a Patent) The kite sold in quite large quantities. I was advised by the American Patent Office, that I could fight the case, but it would probably not be worth the cost. I was of the understanding that if something was on public display, it could not be retrospectively patented. Am I wrong in thinking this?