Jean-Étienne Liotard (22 December 1702 – 12 June 1789) was a Genevan painter, pastellist, printmaker, art theorist and art dealer. Born in the Republic of Geneva as the son of exiled French Huguenots, he spent most of his career working in cities such as Rome, Istanbul, Paris, Vienna, London, Amsterdam and other cities. He is best known for his detailed, strikingly naturalistic portraits in pastel and Orientalist scenes of life in Turkey.
I’m pretty sure he was a dealer, not just of art.