Armstrong collected samples of rocks and dust from the surface of the moon during his historic landings. What later happened to his keepsakes was unknown, until now.

The bag was lost for decades, until it was discovered in 2003 in the garage of Max Ary, who managed the Cosmosphere Space Museum and Research Center in Kansas. Ary was charged for stealing space artifacts and sentenced to 36 months in federal prison. The bag was returned to the U.S. government - who once again, lost it.

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It was mislabeled as an item from the 1972 Apollo 17 mission, as reported by Ben Guarino. The value of them dropped due to the mislabel, as sample sacks from Apollo 17 weren’t used to collect moon rock.

A Sotheby's spokesperson said: "The true history of the bag went unknown for decades until just a year ago. [The bag] was offered three separate times in 2014 by a small auction house on behalf of the US Marshall's service, garnering not a single bid. It was relisted again in 2015."

In 2015, Nancy Carlson, who consigned the bag to Sotheby's for the auction this July, bought the bag at auction for $995.

In order to have her purchase identified, Carlson went to the Johnson Space Center in Houston. Here, it was confirmed they were in fact part of the Apollo 11 mission.

NASA kept the bag, which led Carlson to seek legal action to have returned. Carlson was successful, and the bag was returned to her this February. NASA wanted to put the bag in a museum collection, which they might be able to now do, as Sotheby's New York has announced it will be auctioned in their Space Exploration auction on 20 July. It has been estimated to sell for up to $4 million. Carlson has said she will donate some of the money raised from the auction to charity.