1939 U.S. Christmas Slogan Seals Block, block of 16, perf. 12 1/2, full gum, F, MNH. Issued 1939 by the National Tuberculosis Association. These Slogan Seals are from a Christmas Seals sheet with a printer's mark of either "S", "D", or "U". Fresh, never folded, shipped flat.
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.