John Mills wears a Jaeger-LeCoultre Reverso

In Above Us the Waves (1955), Commander Fraser keeps his watch flipped the wrong way round, its dial turned in against the wrist and a plain back of steel facing out. John Mills plays Fraser, a Royal Navy officer who argues that the way to reach the German battleship Tirpitz, holed up in a Norwegian fjord, is to go in small and underneath: first with Chariot human torpedoes, then with the X-craft midget submarines whose crews steer beneath the hull to lay their charges. Ralph Thomas directed it from the 1953 book by C.E.T. Warren and James Benson, and Donald Cameron, who took X-6 under the real Tirpitz in 1943 and won the Victoria Cross for it, advised the production.

It is worn that way for a reason: the case slides in its frame and turns over, hiding the crystal and showing the metal, which suits an officer forever climbing in and out of a steel hatch. Watch writers, Worn & Wound among them, read it as a Jaeger-LeCoultre Reverso.

Jaeger-LeCoultre built the first Reverso in 1931 for British army officers in India who kept smashing their watch glass at polo. René-Alfred Chauvot filed the patent for the swivelling case that March, and the name is Latin for "I turn." So the watch guarding Fraser's crystal inside a midget submarine was drawn up to survive a polo mallet on the playing fields of British India.

The brand is the part that stays a notch short of certain. You cannot read a dial signature in a 1955 black-and-white print, and the reversible case was never Jaeger-LeCoultre's alone: from 1938 Hamilton sold a licensed near-twin, the Otis, paying Jaeger-LeCoultre sixty cents a watch for the right to build it. Flipped to its back, the two are the same blank rectangle of steel.