Mia Sara wears a Cartier Tank

John Hughes set Ferris Bueller's Day Off in the affluent suburbs of Chicago's North Shore, and Sloane Peterson, Ferris's girlfriend played by Mia Sara, belongs to that world. A gold watch shows on her wrist during the day around the city, though it never turns far enough toward the camera for the dial to read.

It has been identified as a Cartier Tank, the rectangular dress watch Louis Cartier designed in 1917, but the specific model is unsettled. A crowdsourced listing calls it a Tank Solo, a reference Cartier did not make until 2004, so it cannot be the watch in a 1986 film. A period-correct candidate is the Must de Cartier Tank, the vermeil line Cartier sold through the late 1970s and 1980s. No watch publication has resolved it, and the only identifications come from crowdsourced sites.