Chronicled in John Brewer's book "The American Leonardo," an intriguing and controversial portrait recently underwent pigment analysis to determine its age. Lead-tin yellow and double red pigments point to an origin in 17th c. France. Thus, 21st-century technology has dashed any hope that the painting is Leonardo da Vinci’s work, but its appearance at Sotheby’s, where it is being sold with an estimate of $300,000-500,000 on Jan. 28, has raised many unanswered questions...