An early Renaissance painting by the Italian master Cimabue goes under the hammer Sunday, a few weeks after the rare artwork was found hanging in an unsuspecting elderly Frenchwoman's kitchen.
"Christ Mocked," by the 13th-century artist also known as Cenni di Pepo, has been valued at four to six million euros in what could be France's biggest art sale of the year.
Art experts at Turquin in Paris used infrared reflectology to confirm that the tiny unsigned work, just 26 by 20 centimetres (10 by 8 inches), is part of a larger diptych from 1280, when Cimabue painted eight scenes of the passion and crucifixion of Christ.
Only two other elements of the diptych are known to exist: "The Flagellation of Christ" at the Frick in New York, and "The Virgin and Child with Two Angels" at the National Gallery in London.
The "Virgin" was valued at 7.5 million euros when it was given to the museum in 2000 in lieu of inheritance taxes by a British aristocrat who found it while cleaning out his ancestral seat in Suffolk.
The French painting's elderly owner in Compiegne, northeast of Paris, thought it was just an old religious icon when she sought an appraisal from auctioneers at Acteon, the house organising the sale in nearby Senlis.
"The style, the ornamentation of the gold background, the matchings of the backs of the panels and the overall conditions of the three confirms that they were part of the left side of the same diptych," Acteon said.
It was found to be in excellent shape, though covered in grime from having been displayed right above a cooking hotplate.
Historians say only about a dozen works on wood -- all unsigned -- are thought to have been made by Cimabue, more known for his mosaics, frescoes and altarpieces.
His more natural and nuanced depictions marked a turning point for Italian painters still influenced by highly stylised Byzantine art.
Art historians consider him a trailblazer for the creative Renaissance that would flourish under greats like Giotto, one of Cimabue's pupils.
Since Friday, the painting has been on public display at the city hall in Senlis.