In 1957, Piaget introduced its ultrathin Caliber 9P, a hand-wound mechanical movement measuring only 2 mm thick. To underscore its accomplishment, the Geneva watchmaker crafted a watch with the movement that was slim enough to be housed in a partly hollowed-out $20 gold coin. The company recently reissued the Caliber 9P and placed it in a limited series of Altiplano pocket watches (see “Pocket Protectors”) and in the Piaget secret case-spring coin watch (www.piaget.com). Piaget will produce only 20 of the 0.14-inch-thick coin watches, 10 set in 24-karat-gold dollars and 10 in yuan. Both types are priced at $18,000 each.