A lot of 8, vintage 1978 American 15 cent stamps, part of the Fort McHenry Flag issue, hold a special distinction due to a printing error, specifically, the omission of the gray color. The absence of this color within the stamps design creates a notable variation that distinguishes these stamps as error prints. The Fort McHenry Flag issue pays homage to an iconic moment in American history, commemorating the flag that inspired the national anthem. Vintage American Stamps And Philatelic Collectibles.