Matthew McConaughey wears a Hamilton Khaki Aviation

Most movie watches are props. Cooper's Hamilton is the plot. Christopher Nolan built the climax of Interstellar around a father communicating gravitational data to his daughter across space and time through the second hand of a watch, this watch, a Hamilton Khaki Aviation Pilot Day Date Auto that Cooper gives to Murph before he leaves for the wormhole. When Cooper reaches the tesseract inside the black hole, the watch becomes a transmitter. The most important message in human history arrives as Morse code ticked out by a second hand.

Hamilton designed two watches for the production: the Khaki Aviation Pilot Day Date that Cooper wears, and the Khaki Field Murph, the one he leaves behind with his daughter. Nolan wanted an American brand with aviation heritage, which narrowed the field considerably. Hamilton has been making pilot watches since the 1910s and supplied navigation instruments to the U.S. military through both World Wars. The watch is a 42mm automatic with an 80-hour power reserve and a black dial built for legibility, the kind of watch a former NASA test pilot would actually own.

Most films use watches as wardrobe. Nolan used this one as a transmitter, a plot device, and the emotional anchor of the final act. He gave the Hamilton more close-ups than most characters get dialogue.