1952-5px, 1952 U.S. National Christmas Seals, Imperforate Proof Sheet of 100 seals, No UL, pm "F", F, No Gum. Firm paper, fresh, never folded, shipped flat. Scan is an example. Full scan of front and back available upon request.
Issued 1952 by the National Tuberculosis Association (NTA). Designed by Thomas Darling. Image of a candle and double-barred cross. Printed by the Fleming-Porter Co.
Imperforate sheets have no perforations or rouletting at all.
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.