NEW YORK (AP) -- While removing an old backing from a Paul Cezanne watercolor in preparation for a major auction next week, Christie's says it made an exciting discovery -- a pencil drawing by the French post-impressionist artist on the reverse side of the painting.
The watercolor, "Trees Along A Road," has been in the collection of a New Orleans family since 1956.
The drawing also offers a clue to the probable date of the watercolor's execution that had previously been unclear. It looks similar in composition to an 1884 painting in the collection of the Norton Simon Museum in Pasadena, California, titled "Chestnut Trees and the farm at Jas de Bouffan," the auction house said.
Jas de Bouffan was the artist's family's country estate in Aix-en-Provence in France, a frequent subject of his paintings.
"Cezanne wasn't in the habit of dating things. ... but because he would use both sides of a paper at the same time, it brings us closer to the probable date of execution for both sides of the sheet," said Conor Jordan, Christie's impressionist and modern art specialist.
The drawing depicts three rounded tree trunks in the foreground and foliage and architectural elements in the background.
Earlier this year, similar discoveries were made on the backs of two Cezanne watercolors in the collection of the Barnes Foundation in Philadelphia. The two unfinished sketches -- one graphite and the other watercolor -- also were found after paper backing was removed.
The discovery at Christie's was made two weeks ago during a routine conservation in advance of its Nov. 12 evening sale of impressionist and modern art where the "Trees Along A Road" is estimated to bring between $400,000 and $800,000.
Whether the discovery will jack up the price is hard to tell, but "it will excite the people who buy Cezanne drawings ... It will make it more desirable and a great addition to anyone's collection," said Jordan.
"It is a very interesting discovery for scholars," because Cezanne's works are very well-recorded, said David Nash, a Cezanne expert. "The drawing is not recorded until now."
Additionally, the back of the sheet also has two inscriptions that read: "Voll." It's an abbreviation for Cezanne's dealer, Ambroise Vollard, and would indicate that that the two-sided sheet was among the works he selected when Vollard divided a large group of Cezanne's drawings with another dealer after the artist's death in 1907.
The watercolor is being sold by Alexandra Stafford, of New Orleans, whose parents acquired it almost 60 years ago.
"We didn't know it had a drawing," she said in a telephone interview. "When Christie's suggested we update the framing and put on proper backing ... when they did that -- boom -- there was a drawing in the back."