What is a 1933 Saint-Gaudens 20 gold coin with double eagles and the word copy on it worth?

Most likely. They were demonetized and destroyed sometime in 1933. There was documentation proving that one was legally exported before the gold act was passed. It is valued in 7 figures. Ten more are currently held by the Treasury department but the people who sent them to verify their authenticity is suing to have them returned. It will be interesting to see how this is resolved.