Long before anyone had even heard of Jane Birkin and her eponymous bag, Louis Cartier's Tank watch was the cult object du jour. Brigitte Bardot, Elizabeth Taylor, Fred Astaire, and Andy Warhol were all seduced by its tick. So enamored was silent-film star Rudolph Valentino, he refused to remove his Tank while filming--even if it made no sense in the scene. Cartier's design inspiration was the world's first armored tank, which debuted in 1916; the casing around the watch's face has mimicked the look of the machine ever since. Now, to celebrate the 162-year-old jeweler's centennial in the States, a diamond-studded limited edition of the Tank is poised to start a luxurious revolution.