Only one man was able to be the very first to walk on the moon. Now, an auction that's just as singular. On July 20, Sotheby's will auction a bag containing traces of moon dust, which a Chicago-area woman picked up for $995 and which is expected to sell for as much as $4 million.

It's an extreme price befitting the extreme story behind the bag, which Neil Armstrong used to store lunar rocks collected from the moon after the Apollo 11 landing.

The bag's convoluted history includes the 2003 FBI raid on the home of Max Ary, the former director of a Kansas space museum. The Wall Street Journal reports the director was convicted of theft tied to his auctioning of some NASA artifacts, and his possessions were seized, with some auctioned for restitution—which is when the goof happened.

How Ary ended up with the bag is still a bit murky, but what is clear is that the government auctioned it as "one flown zippered lunar sample return bag with lunar dust ('Lunar Bag'), 11.5 inches; tear at center. Flown Mission Unknown," and Nancy Lee Carlson scooped it up.

The Sotheby's listing explains Carlson wanted to learn more about her bag's history, so she sent it to NASA; officials there realized what had happened and refused to return it, until a court forced them to earlier this year.

"This is a once-in-a-lifetime event," Sotheby's Cassandra Hatton tells the Chicago Tribune, which explains why: This may be "the only privately held object of its kind in the world," at least as far as legally sold lunar objects go.

Carlson plans to donate some proceeds to charity and set up a scholarship at her alma mater, Northern Michigan University. (This widow can sue over NASA's brutal sting operation of her.)

This article originally appeared on Newser: NASA's Goof Could Mean $4M Windfall for Illinois Woman