Tiny numbers and letters have been discovered painted into the eyes of the Mona Lisa prompting an investigation by art historians.
Members of Italy's National Committee for Cultural Heritage say the letters and numbers can be seen when magnifying high resolution images of the Mona Lisa'a eyes, the Daily Mail reports.
"To the naked eye the symbols are not visible but with a magnifying glass they can clearly be seen," Silvano Vinceti, president of the Committee, was quoted as saying.
"In the right eye appear to be the letters LV which could well stand for his name Leonardo Da Vinci while in the left eye there are also symbols but they are not as defined."
"It is very difficult to make them out clearly but they appear to be the letters CE or it could be the letter B - you have to remember the picture is almost 500 years old so it is not as sharp and clear as when first painted."
"While in the arch of the bridge in the background the number 72 can be seen or it could be an L and the number 2."
The discovery of a 50-year-old book in an antique shop was the catalyst for the discovery of the symbols.
"We are only at the start of this investigation and we hope to be able to dig deeper into this mystery and reveal further details as soon as possible," Mr Vinceti told the Daily Mail.
"It's remarkable that no-one has noticed these symbols before and from the preliminary investigations we have carried out we are confident they are not a mistake and were put there by the artist."
Mr Vincetti has travelled to Paris to examine the painting where it is on display in the Louvre.