1924, WX32, 1921 U.S. Christmas TB Seals Block, perf. 12 1/2, fresh, full gum, F, MNH. Scans of front and back provided upon request.
Issued by the National Tuberculosis Association (NTA). Designed by George V. Curtis. Colors: blue, red, and yellow; size: 18x24mm, with perf 12 1/2.
Christmas Seals are also known as TB Seals, and are usually classified as Charity Seals, or Cinderella Stamps..