This United States one dollar bill holds the signatures of the three Apollo 11 astronauts (Neil Armstrong, Michael Collins, and Buzz Aldrin) in addition to one other signature, that of a certifying official from the National Aeronautic Association (NAA), all on the front of the bill. This memento of the historic first human landing on the Moon in July 1969 was part of the official process of certifying the flight.
Before human spaceflights, the NAA had the astronauts autograph dollar bills, witnessed by the NAA official for the flight. The bills were then placed aboard the spacecraft. After the mission, recovering the identifiable bills served "as the basis for certification of the identity of the astronauts on each of the flights."
The NASA Johnson Space Center transferred this bill to the National Air and Space Museum in 1976.