1939-2pxB, 1939 U.S. National Christmas Seals, Imperforate Proof Sheet, pm "S", F, No Gum. Issued 1939 by the National Tuberculosis Association (NTA). Designed by Rockwell Kent. Image of an Angel with halo. Firm paper, fresh, never folded, shipped flat.
Sheet of 100 (10x10) seals. 96 regular seals, 4 slogan seals located in center of sheet. Seal colors: red, pink, light blue, and ultramarine. Seal size: 171/2x23mm. Strobridge Lithographing Co., second printing, there is a 'S" in the lower right corner of seal #57, and a break in the upper frame on seal #29.
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.