"Christ Mocked" is expected to fetch up to 6 million Euros ($6.59 million) at auction this month, according to Jerome Montcouquil of art specialists Cabinet Turquin, which was asked to carry out tests on the painting after its discovery at the beginning of this summer.

An elderly French woman from the town of Compiegne had kept the rare artwork -- which she thought was a Greek religious icon -- hanging in her kitchen, said Montcouquil. The unsuspecting owner did not
know where the 25.8 x 20.3 centimeter painting came from, he added.

"It didn't take long for us to see that it was an artwork by Italian painter Cimabue. He's a father of painting so we know his work very well," Montcouquil told CNN.

Cimabue is the pseudonym of artist Cenni di Pepo, born in Florence around the year 1240. He is known to have been the discoverer and master of Giotto, widely regarded as one of the greatest artists of the
pre-Renaissance era.

"There are only eleven of his paintings in the world - they are rare."

Montcouquil said the work is part of a diptych made in 1280 when the artist painted eight scenes centered on the passion and crucifixion of Christ.

The style of painting, the gold background, and traces of the old frame helped experts identify the painting as part of the triptych, according to a press release from auctioneers Acteon.

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The pictorial layer remains in "excellent condition" despite accumulating dust, continued the release.

The National Gallery in London is home to another scene from the work, "The Virgin and Child with Two Angels," which the gallery acquired in 2000.

It was lost for centuries before a British aristocrat found it in his seat in Suffolk, according to AFP.

Another -- "The Flagellation of Christ" -- can be found at the Frick Collection in New York.

"They are all made with the same technique on the same wood panel so you can follow the grain of the wood through the different scenes," said Montcouquil.

The "Apollo and Venus" painting by 16th-century Dutch master Otto van Veen (1556-1629) was discovered in the closet of an art gallery in Iowa, and is likely worth over $4 million.

"We also used infrared light to be sure the painting was done by the same hand. You can even see the corrections he made."

The painting had been hanging above a hot plate used for cooking food, but is now set to go under the hammer on October 27 at the Acteon auction house in Senlis, north of Paris, according to AFP.
It will be the first ever Cimabue painting to be auctioned, according to Montcouquil. CNN