The one and only...until now.
It's entitled 'Joconde Nue' and 'Monna Vanna,' and French scientists studying the charcoal drawing of a topless woman with a face similar to that of the Mona Lisa, the best known portrait in the world exposed at the Louvre Museum in Paris, believe it was at least partially painted by Leonardo Da Vinci.
The nude Mona Lisa is believed to have been a sketch drawn before the most famous of all portraits.
For the past month, the drawing has been undergoing an appraisal in Paris at the Center for Research and Restoration of the Museums of France. The experts have concluded that the figure might be a nude sketch of Mona Lisa drawn just before Leonardo painted the iconic portrait.
They also think that the drawing of the Joconde Nue, until now thought to have been done by Leonardo’s students, was “at least in part” done by the Italian master himself.
"The hatching on the top of the drawing near the head was done by a right-handed person," Bruno Mottin, a conservation expert explained to Le Parisien. "Leonardo drew with his left hand.”
The piece, proved to be an original from Leonardo's studio and not one of the 20 or so copies that exist around the world, has been at the Condé Museum in Chantilly, north of Paris, for more than 150 years since it was bought for 7,000 francs in 1862 by the Duke d'Aumale.
“It has a quality in the way the face and hands are rendered that is truly remarkable," curator Mathieu Deldicque told the AFP. "It is not a pale copy."
He also said the drawing was done “in parallel with the Mona Lisa, which was painted around 1503 at the end of Leonardo's life," and that it was very likely in preparation for an oil painting.
Although there are many differences, experts have noted that the torso and the hands are almost identical, and identify similarities in the enigmatic smile in the two paintings, which also are quite close in size, with the charcoal drawing showing pierced holes that suggest it could have been used as a backdrop to trace a second image.
The history of the Mona Lisa, according to the Louvre Museum, continues to be shrouded in mystery. "Among the aspects which remain unclear are the exact identity of the sitter, who commissioned the portrait, how long Leonardo worked on the painting, how long he kept it, and how it came to be in the French royal collection," the museum details on its website.
The portrait was begun in Florence around 1503 and its thought to be of Lisa Gherardini, wife of a Florentine cloth merchant named Francesco del Giocondo - hence the alternative title, "La Gioconda." Leonardo seems to have taken the portrait to France rather than giving it to the person who commissioned it.
The Louvre curators hope to have answers to all the enigmas surrounding the erotic double of the best-known painting in the world in time for the start of the 500-year anniversary of Leonardo’s death in 2019. The painting won’t be available for public viewing until the research is completed.