Cillian Murphy wears a Hamilton Lexington

The Hamilton Lexington had a short production run, it went into production just before Pearl Harbor and stopped not long after. Christopher Nolan chose it for the transitional period of Oppenheimer's life, the early 1940s when the physicist moved from academic research to the Manhattan Project. The Lexington has applied numerals and a restrained design, sitting between the ornate Cushion B of the 1930s and the cleaner Endicott that carries the Los Alamos and hearing sequences.

Hamilton stopped making civilian watches during World War II, converting their Lancaster factory to military production. The Lexington belongs to the last moment of peacetime manufacturing before that conversion, which gives it an unintentional significance in a film about the bomb. Oppenheimer wore an American watch made by a company that would soon be making marine chronometers and military-issue navigation instruments for the same war he was trying to end with physics.

The Lexington is the rarest of the three Hamilton watches worn in the film, its abbreviated production run means fewer survive, and finding one in wearable condition would have required access to Hamilton's own archives or a very patient collector.