Unlike the big, heavily branded jewellery firms—Cartier, Graff, Harry Winston—JAR has just one small shop, a blank-fronted place in a dull plaza in Paris, and doesn’t spend a sou putting adverts in glossy magazines. Or indeed anywhere. Because secrecy is JAR’s secret weapon. You won’t find the shop’s address in any directories; as a rule, would-be customers have to be vetted and introduced, like Freemasons, by a friend. Rosenthal himself maintains a Garbo-like silence in the face of the press, giving only a handful of interviews in his 37-year career and—at least partly for reasons of security—never, ever allowing himself to be photographed.