Illustration of the seal of the U.S. w:Federal Civil Defense Administration from s:Executive Order 10350, which defined the seal.  The design is described there as:
 On a disk of Defenders Blue a white triangle superimposed by a shield of the coat of arms of the United States proper, all encircled by a white band edged in Defenders Blue containing the inscription "FEDERAL CIVIL DEFENSE ADMINISTRATION" in scarlet letters.
Vector conversion of File:US-FederalCivilDefenseAdministration-Seal-EO10350.jpg, using Inkscape and other tools.
U.S. Government (This rendering by Hydrargyrum)