Henry Cavill wears a Cyma Dirty Dozen Field Watch

Henry Cavill carries a suppressed Sten in The Ministry of Ungentlemanly Warfare, and on the wrist gripping it sits a small field watch on an olive strap. He plays Major Gus March-Phillipps, the Small Scale Raiding Force officer who led Operation Postmaster, the Special Operations Executive raid that slipped into the harbour at Fernando Po on 14 January 1942 and sailed off with the Italian merchant ship Duchessa d'Aosta while her officers were at a party ashore. Guy Ritchie adapted the film from Damien Lewis's book about Churchill's irregulars, and his costume designer went looking for the genuine article.

The watch is a Cyma, one of the so-called Dirty Dozen: the twelve Swiss firms (Buren, Cyma, Eterna, Grana, IWC, Jaeger-LeCoultre, Lemania, Longines, Omega, Record, Timor and Vertex) that built to a single British military standard, the W.W.W., for Watch, Wristlet, Waterproof. The brief called for a matte black dial, Arabic numerals, luminous hands, a small seconds register and a shock- and water-resistant steel case, and about 145,000 watches were delivered against it. Costume designer Loulou Bontemps told GQ she bought a genuine vintage Cyma, along with a Jaeger-LeCoultre from the same Dirty Dozen set, from the dealer Specialist Watches, and that Cavill, who works closely on his costumes and chose the pieces himself, wears the Cyma in the film.

The W.W.W. standard, though, was not issued until 1945, and the watches reached British troops only afterward, as the war was ending. Operation Postmaster happened in January 1942, three years before any Dirty Dozen reached a soldier's wrist. So the watch now treated as the definitive British military field watch is, for this raid, an anachronism: the real thing, built to a genuine military spec, but not yet built when March-Phillipps boarded the Duchessa d'Aosta.