75-3x, WX255, ALA National Design 1975 U.S. Christmas Seals Sheet, pm B, full gum, F, MNH. Fresh, full gum, shipped flat. Scan is of front of sheet.
Issued 1975 by the American Lung Association (ALA). Designed by school children from each state, Puerto Rico, Virgin Islands, D.C., and Samoa/Guam. Sheet of 54 (6x9) seals, SE3S, perforated margin at top, multicolored. Seal size: 30x25mm, perf 11. Printer's Mark B on seal #28 indicates Fleming-Potter Company. GAU Union Label in upper left top margin.
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.