1940-2pxB, 1940 U.S. National Christmas Seals, Imperforate Proof Sheet, pm whiter "S", F, No Gum. Issued 1940 by the National Tuberculosis Association (NTA). Designed by Felix Martini. Image of three children singing. Firm paper, fresh, never folded, shipped flat.
Sheet of 100 (10x10) seals; 3 slogan seals and 97 regular seals. Slogan seals show one of the three children on each seal. Color: yellow, blue, red, and ultramarine, green margins. Seal Size: 171/2x23mm. Printed by Eureka Specialty Printing Co.
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.