Mona Lisa replicas and reinterpretations
After restoration, the Prado's "Mona Lisa" revealed details covered by previous restorations and layers of varnish.
Furnishings and fabrics were enhanced, as well as landscape and facial features.
It is anticipated that such revelations may offer further insight into Leonardo's original.
Experts at the Louvre reportedly supported the Prado museum's findings.
The Prado replica was subsequently transported to the Louvre in 2012 to be displayed next to "Mona Lisa" as part of a temporary exhibition.
Two nude paintings bearing similarities to Leonardo da Vinci's original were part of a 2009 exhibition of artwork inspired by "Mona Lisa".
Displayed at the Museo Ideale in Leonardo's hometown of Vinci, near Florence, some believe one of the paintings – dating from Leonardo's time – to be the work of Leonardo himself, and it has at times been credited to him.
Other experts theorize the painting, one of at least six known to exist, may be just another copy painted by "followers" of Leonardo.
Scholarly dispute persists as to artist, subject and origin.
The nude in question, discovered behind a wall in a private library, reportedly belonged to an uncle of Napoleon Bonaparte, who owned another of Leonardo's paintings.
Facial features bear only vague resemblance, but landscape, compositional and technical details correspond to those of the "Mona Lisa" known worldwide today.
Seymour Reit
Reit wrote over 80 books, primarily for children, on a variety of historical, technical, natural, and other subjects. One of his titles for adults, "The Day They Stole the Mona Lisa", written in 1981, is about the theft of the Mona Lisa from the Louvre in 1911. In the book, Reit asserted that there were "two" genuine "Mona Lisas" in the world: the one in the Louvre, and an earlier version of the work painted by Leonardo da Vinci which was being held in a bank vault in New Jersey (the so-called "Vernon Mona Lisa"). A long-planned movie adaptation of the book has never materialized, although the Internet Movie Database lists a movie by the same title tentatively planned for 2009.