London, UK - Ruby slippers worn by actor Judy Garland in the classic film The Wizard of Oz will be sold at auction next month, nearly 20 years after they were stolen.

Heritage Auctions showed off the magical footwear in London before they go under the hammer in Dallas on December 7, with predictions they could sell for up to $3 million.

"They are legendary like no other," Nikki Hale, manager of special projects at Heritage, told AFP of the distinctive sequin-covered court shoes, which are topped with bows.

"The Wizard of Oz really stands the test of time as a cult classic, iconic film that anywhere across the world, people know what The Wizard of Oz is."

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"You see them when she's clicking the heels to go home. You see them when she starts her adventure, when she goes down Munchkinland," Hale added.

"They are absolutely the Holy Grail as far as movie memorabilia."

Only four pairs made for the 1939 film still survive and those on sale have belonged to a collector since 1970.

They were kept in the Judy Garland Museum in her hometown of Grand Rapids, Minnesota until they mysteriously disappeared in 2005.

Despite a six-figure reward and the involvement of the FBI, it was not until 2018 that they were finally tracked down.

"They were recovered, apparently buried in a Tupperware [box] underground," said Hale.

The perpetrator of the theft, Terry Martin, admitted to taking them and said he did so because he believed they were encrusted with real rubies.

Now 76, he was given a suspended prison sentence in January this year.

Other memorabilia from The Wizard of Oz will also be on sale, including Garland's wigs, film posters, and photographs as well as other items such as a wooden game board from Jumanji with the late great actor Robin Williams.