A previously unknown foot sketch by Michelangelo has sold for $23 million (£16.9 million) at Christie’s, more than ten times its original estimate, with experts identifying it as a study of the Libyan Sibyl later painted on the Sistine Chapel ceiling. According to the auction house, the work surfaced after an unsuspecting owner submitted a photograph for an auction estimate, only to discover the drawing’s true value.The anonymous owner, based on the US West Coast, told Christie’s he had inherited the drawing from his grandmother and that it had been passed down through his family in Europe since the late 1700s.Andrew Fletcher, global head of Christie’s Old Masters Department, described the discovery as “one of the most memorable moments” of his career, as cited by the BBC.A specialist in Christie’s Old Master Drawings Department, Giada Damen, used infrared reflectography to examine the work, revealing additional drawings on the back of the sheet that also resembled Michelangelo’s style.The drawing offers rare insight into Michelangelo’s working process, Christie’s said, noting that most of his sketches have been lost over time, some burned by the artist himself, others destroyed by early collectors or during the course of his work.Only two known sketches related to the Libyan Sibyl survive today, one held by the Ashmolean Museum in Oxford and the other by the Metropolitan Museum of Art in New York. In total, only around 50 studies for the Sistine Chapel are known to exist, and none had previously appeared at auction. The discovery of the sketch triggered a bidding war, with the work selling for nearly 20 times its original estimate and becoming the most expensive Michelangelo drawing ever sold at auction, according to Christie’s.Although the sketch was previously unknown to scholars, several clues pointed to its provenance.Michelangelo’s name appears at the bottom left of the sheet in handwriting matching the inscription on the Metropolitan Museum’s example, and after months of research by Giada Damen, leading experts on the artist unanimously agreed that the drawing was by Michelangelo, Christie’s said, as cited by CNN.