1932-1p1x, 1932 U.S. Christmas Seals, Plate B, Imperforate Proof Sheet of 100 seals, F, No Gum. Firm paper, fresh, never folded, shipped flat.
Issued 1932 by the National Tuberculosis Association. Designed by Edward F. Wolkmann. Image of Carolers in snow. Sheet of 100 (10x10). Seal colors: yellow, red, blue, and ultra. Eureka Printing, Plate 'B" a diagonal red line across the white frame at the four corners of the sheet, on the outer corners of seals #1, 10, 91, and 100.
Imperforate sheets have no perforations or rouletting at all.
Christmas Seals are also known as TB Charity Seals, and are usually classified as Charity Seals, or Cinderella Stamps.