US #1597 15¢ Fort McHenry Flag Error - Imperforate vertical pair

1978 Mint Vertical Imperforate Pair
One of the greatest thrills of collecting is discovering errors - those unintentional printing mistakes that find their way into our stamp collections. This sheet version of the 1978 15¢ Fort McHenry Flag stamp is completely missing its perforations. As a vertical pair, it can be easily identified as the sheet version since the imperforate coil version of the same design can exist only as a horizontal pair. Add this amazing imperforate error pair to your collection at an irresistible price! (U.S. #1597e imperf pair)