26-2xB, WX38, 1926 U.S. Christmas Seals, Type 2, pm F, full gum, F, MNH. Sheet has never been folded, shipped flat.
Issued 1926 by the National Tuberculosis Association. Designed by George V. Curtis. Image of the Cross of Lorraine on Shield. Offset by United States Printing & Lithograph Co. Printer's mark: a small dark dot above the upper left corner of seal #56. This scarce sheet of 100 (10x10), SE4S, in blue red, yellow, and black. Seal size: 18x24mm, perf. 121/2, full gum.
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.