1910-1, WX6, 1910 U.S. Christmas Seal, F, SE, MNH, The 1910 Christmas Seal was issued by the American National Red Cross. Designed Frances Thompson. Lithographed by Strobridge Lithographing Co. Size 22x22MM, perf. 12. There was just one type. Scan is an example of the seal.
Note from Green's Catalog: "The designs this year are spaced extremely close together within the sheet and examples with the designs clear of the perforations on all four sides are scarce."
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.