 However, by 1993, Frank Zöllner observed that the painting surface had never been trimmed; this was confirmed through a series of tests in 2004.In view of this, , curator of 16th-century Italian painting at the Louvre, states that the sketch and these other copies must have been inspired by another version, while Zöllner states that the sketch may be after another Leonardo portrait of the same subject.The record of an October 1517 visit by Louis d'Aragon states that the "Mona Lisa" was executed for the deceased Giuliano de' Medici, Leonardo's steward at the Belvedere Palace between 1513 and 1516—but this was likely an error.