I have a stamp that is a 3c Green Printed on both side. The catalogue says its worth $20,000.00, however I find it hard to believe that I have a rare stamp. Was hoping that someone could give me more information.
GeoffHa is correct. This stamp only looks like it was printed on the back - in reality the sheet of stamps that this stamp came from was deposited on another sheet that was still wet from printing. This is called "set-off".