21-3p, 1929 U.S. National Christmas Seals, Imperforate pair, full gum, F, MNH. Issued 1921 by the National Tuberculosis Association (NTA). Designed by George V. Curtis. Image of Santa and Chimney. Typographed by Zeese-Wilkinson, Inc.
Imperforate Pairs are seals from sheets that have no perforations or rouletting at all. Proofs and essays are most likey imperforated.
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.