28-1xB, WX44, 1928 U.S. Christmas Seals Sheet, full gum, F, MNH. Fresh, firm paper, full gum, bright colors, shipped flat.
Issued 1928 by the National Tuberculosis Association (NTA). Designed by John W. Evans. Image of Ship sailing in sea. Sheet of 100 (10x10), Perf. 121/2, yellow, red, black, and blue. Seal size: 18x24mm. Printer's Mark: there is a slanted blue line on margin above "N" of "Greetings" on seal #10, which indicates that the sheet was printed by Eureka Speciality Printing Co.
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.