Apollo 11 astronaut Michael Collins has revealed a previously unseen photo of the famous Moon landing crew members that he “found at the bottom of a box.”

The photo shows Collins, Neil Armstrong and Buzz Aldrin and what appears to be a model of the Moon. Collins, who was the Apollo 11 command module pilot, has autographed the photo.

"The crew. Found this at the bottom of a box. Don't think it was ever used by @NASA," Collins tweeted.

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The Apollo 11 astronaut tweeted the image last week with the hashtag #TBT for ‘Throwback Thursday.’ July 20, 2019, marks the 50th anniversary of the Apollo 11 mission.

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Collins remained in Apollo 11’s Columbia Command Module while his fellow crew members Armstrong and Aldrin famously descended to the Moon’s surface in the Eagle Lunar Module.

Fox News has reached out to NASA with a request for comment on this story.

The Columbia Command Module is now in the collection of the Smithsonian National Air and Space Museum. The module is part of "Destination Moon: The Apollo 11 Mission," a traveling Smithsonian exhibit that is at the Museum of Flight in Seattle until Sept. 2, 2019. The command module will go back on display at the Smithsonian in 2022 when the museum's new Destination Moon exhibit opens.

The descent stage of the Eagle Lunar Module remained on the Moon while the module’s ascent stage carried Armstrong and Aldrin back to the Columbia Command Module. After the astronauts safely docked with the Command Module, the ascent stage was jettisoned and programmed to crash into the Moon, according to the Smithsonian.

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The Smithsonian National Air and Space Museum is showcasing a host of stunning artifacts to celebrate the 50th anniversary of Apollo 11. On July 16, for example, the museum will place Neil Armstrong's spacesuit back on display.

Collins, an Air Force fighter pilot and test pilot, joined NASA in 1963 as part of its third group of astronauts. In addition to Apollo 11, he also piloted the Gemini 10 mission in 1966. Although Collins never made it to the surface of the Moon, he logged 266 hours in space during his two space flights, according to NASA.

Only 12 men, all Americans, have walked on the Moon.

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Apollo 16 astronaut Charles Duke recently told Fox News that he wants to see future generations of astronauts build on the incredible legacy of the Apollo program.

Duke became the 10th person to set foot on the lunar surface after the module carrying him and John Young landed on the Moon on April 20, 1972. At 36 years and 201 days old, the astronaut was the youngest person to walk on the Moon.

Duke, Aldrin, Apollo 15 astronaut David Scott and Apollo 17 astronaut Harrison Schmitt are the only living people to have walked on the Moon.

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The Associated Press contributed to this article. Follow James Rogers on Twitter @jamesjrogers