Neil Armstrong, the first astronaut to walk on the moon, kept a secret stash of mementos -- a bag containing small parts from the Eagle lunar landing module -- from that historic mission, it has been revealed.

After he died, his widow discovered the small stowage bag containing parts from the module that Armstrong and Buzz Aldrin piloted to their landing on the moon on July 20, 1969.

Carol Armstrong got in touch with Allan Needell, curator of the National Air and Space Museum's Apollo collection, and told him of the white cloth bag full of "space stuff" that she found inside a closet in the Armstrong's home.

"Needless to say, for a curator of a collection of space artifacts, it is hard to imagine anything more exciting," Needell wrote in a museum blog posting.

He realized she had found "The Purse," a storage bag the Apollo 11 astronauts used to keep repair equipment and other assorted items, he said.

Because the bag's contents are among the very few items brought back from the Eagle's Tranquility Base landing site, they are of priceless historical value, NASA says.

The artifacts in the bag -- wrenches, straps and assorted equipment -- look rather ordinary, with one exception.

Inside the storage bag was a 16mm movie camera, known as the data acquisition camera or DAC.

It's the actual camera used by Armstrong and Aldrin to film their descent and landing and Armstrong's first steps down the lander's ladder for his "small step" for mankind onto the lunar surface.

"Needless to say, for a curator of a collection of space artifacts, it is hard to imagine anything more exciting," Needell posted.

"The 16mm DAC, given the images that it captured, ranks as enormously important," he said.

The bag, known as the "McDivitt purse" after Apollo 9 astronaut James McDivitt who first suggested such a storage item be included in Apollo missions, was transferred from the Eagle landing module to the Columbia command module and brought back to Earth.

In the decades after his moon landing, Armstrong never made mention of the historic bag and his contents casually tucked into a closet in his home.

How it ended up in his possession following the Apollo 11 moon landing is not knows, but astronauts often held onto small used and extra parts from their mission capsules as personal souvenirs.

Although technically the property of NASA, the bag and its contents are on loan to the National Air and Space Museum and will be put on public display.