You are bidding on a unique vintage, metal, maybe cast iron, with bronze finish, heavy souvenir key for the 1933 Chicago's World Fair, Reads on the top with picture - Hall of Science, Chicago and on the back, Travel and Transport 1933. One the lower key part it reads: Key to Chicago World's Fair and on the other side - A Century of Progress 1933. Really nice antique piece with great patina. About 8 1/4 inches long. 

Look at the picture.