Simply a cheap Mona Lisa postcard with facial hair pencilled on & abbreviated vulgarity for its title, this 1919 French-American piece and it’s many subsequent versions set the high art world on fire. It became one of the building blocks for bold conceptual art that violently rejected every convention of the Western Art tradition. The 1964 version sold in a Paris auction for $750,000 in 2017. Christened “readymade” art by Duchamp, it involved taking ordinary items, altering and placing them in appropriate settings, creating art from the mundane.