28-3x, WX46, 1928 U.S. Christmas Seals Sheet, full gum, F, MNH. Fresh, shipped flat.
Issued 1928 by the National Tuberculosis Association. Designed by John W. Evans. Image of Ship sailing in sea. Sheet of 100 (10x10), yellow, red, black, and blue. Seal size: 18x24mm. Printer's Mark: on seal #92, Perf. 121/2, there is a red dot on the crest of the left wave, which indicates that the sheet was printed by Edwards and Deutch.
This is mint, never hinged, full gum dealer stock.
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.