A rare, pristine Paul Cezanne watercolor, which has not been seen in public since 1953, is expected to sell for as much as $20 million at auction in May, Christie's said on Tuesday.

The late 19th-century work on paper is one of Cezanne's preparatory studies for his seminal Card Players series of five paintings, Joueurs des cartes.

Its whereabouts had been unknown for decades until it re-emerged from the collection of a doctor in Texas. The auction house found the drawing when it was working with the estate of Dr. Heniz Eichenwald, who died in September at the age of 85.

They were very private people, Christie's president Marc Porter said, adding the work had been in the family for eight decades.

The art was for their enjoyment rather than for public display. It was not hidden away in the house, it was enjoyed. But it wasn't as important for their social position as it was for them, Porter said.

Last year the catalog from the Metropolitan Museum of Art's exhibition of Cezanne's Card Players listed the work as whereabouts unknown.

Sharon Kim, Christie's international director of Impressionist and modern art, said it had been feared the work had been lost to history by collectors and scholars. When a Cezanne watercolor was mentioned in the estate Christie's was intrigued.

We checked and found it fit the description of the 'whereabouts unknown' piece and knew this was really likely it, she said.

The study is most closely linked to the two-figure version of the Card Players series at the Musee D'Orsay in Paris.

You can see the immediacy in the work, like the D'Orsay's. He's working through the process of how he's going to execute this on canvas, Kim explained, adding that it looks like it was painted yesterday.

The colors were astonishing, she added.

The doctor's estate was aware of the work's importance but astounded by it estimated value.

Christie's estimates the work will sell for up to $20 million. It will be the first time in a decade that the leading highlight of its sale of Impressionist and Modern Art has been a work on paper.

The work will be exhibited in Geneva in April before a New York showing ahead of the May 1 sale.

Earlier this week, Sotheby's announced a find of its own, a painting by the pioneering female artist Tamara de Lempicka, which is expected to fetch nearly $5 million at auction.

A West Coast construction company owner had the work in his home for years before being advised it might be a Lempicka.