Leonardo da Vinci’s Salvator Mundi has been in and out of the news. It is the world’s most expensive painting, having sold for $450.3 million dollars at a Christie’s auction in 2017. No one’s seen it for a while, but it’s believed to be somewhere in the Persian Gulf. Or in storage, where the owner can avoid paying duties. It’s been heavily restored, with less than a quarter of its surface original to the late fifteenth or early sixteenth century. It may have been painted by Leonardo with assistance. Actually, it might not be by the artist’s hand at all.