This hatch was part of the Apollo 10 Command Module "Charlie Brown," which was launched in May, 1969, on a "dress rehearsal" for the first planned manned lunar landing mission. The Apollo hatch had to provide a perfect seal for proper cabin pressurization, thermal protection during re-entry, and water-tight conditions during splashdown and recovery. An example of the "unified hatch" designed following the fatal Apollo 204 fire in January, 1967, the Apollo 10 hatch covered the side opening in both the pressurized cabin and the external heat shield that covered the spacecraft. It could be opened from the inside in a matter of seconds.
Stripped after the flight of all components of the mechanical locking system, the Apollo 10 Command Module hatch was transferred to the Smithsonian Institution by the NASA Johnson Space Center in 1977, three years after the transfer of the Apollo 10 Command Module.