Alain Delon wears an Universal Genève Polerouter

Jacques Deray directed La Piscine (1969) from a script he wrote with Jean-Claude Carrière, and cast two former lovers as his leads: Alain Delon and Romy Schneider, who had been engaged in real life and split a few years before filming. They play Jean-Paul and Marianne, whose sun-baked St. Tropez idyll curdles when Marianne's old flame Harry (Maurice Ronet) turns up with a daughter the couple never knew he had, Penelope, played by a 21-year-old Jane Birkin. The film runs on what no one says, jealousy and desire circling the pool in the heat.

Delon wears a Universal Genève Polerouter, a model with real pedigree. Universal Genève, founded in Le Locle in 1894, handed the design to a 23-year-old Gérald Genta in 1954, his first major commission, for a watch to mark Scandinavian Airlines' new polar routes. Genta drew the case; the movement came a year later, when Universal fitted the Polerouter with its caliber 215 micro-rotor, at 4.1mm the slimmest automatic in the world when it debuted in 1955. Delon's is one of those micro-rotor versions, the reference 20357-2, with the lyre-shaped lugs Huguenin Frères made for the line. Universal produced the Polerouter from 1954 to 1969, so the watch on Delon's wrist belonged to the model's final year.