Rolex sources natural stones, hand-selecting them, and then cutting them to size, which means the watchmakers are taking this seriously. "The calibration on these stones is amazing," Dyne said. "I have nothing against the use of stones here." Horological gem setting is no easy feat, with up to 90 percent of each colored stone being disposed of in order to have them fit perfectly into a gradient setting. And all link of this is done in-house.