Before revision: USPS postage stampand "Pluto Fast Flyby" In October 1991, the United States Postal Service released a series of stamps commemorating NASA's exploration of the Solar System.Smithsonian National Postal Museum (date unknown).
After revision: Pluto postage stamp In October 1991, the United States Postal Service released a series of stamps commemorating NASA's exploration of the Solar System.Smithsonian National Postal Museum (date unknown).