This is a beautiful sheet of 6 stamps, issued by Guinea in 2010, commemorating the 80th anniversary of the discovery of the planet Pluto. Also honored on the stamps are American astronomer William Henry Pickering, mathematician & astronomer Percival Lowell, Dutch-American astronomer Gerard Kuiper, Bruno Sicardy from the Paris Astronomical Observatory, American planetary scientist Alan Stern, and U.S. writer & "Dean of Science Fiction" Jack Williamson. The sheet is Michel catalog #7599-604, and is Post Office fresh, mint never hinged, and F/VF.