The Cartier Santos is not merely a watch; it is arguably the founding document of the modern wristwatch era. In 1904, Louis Cartier designed a wristwatch for his friend Alberto Santos-Dumont, the Brazilian aviation pioneer who needed a timepiece he could read without taking his hands off the controls of his experimental aircraft — pocket watches were useless in the cockpit. The result was a square-cased watch with exposed screws on the bezel and integrated strap lugs, a utilitarian aesthetic that was radically modern for its time. Santos-Dumont made the first public powered flight in Europe in 1906 while wearing the watch, cementing its place in history. The Santos was formally commercialized by Cartier in 1978 in yellow gold and steel, and it has been in near-continuous production since, with key references including the Santos Dumont, Santos 100, and the 2018-relaunched Santos de Cartier with QuickSwitch interchangeable strap system. Pre-owned Santos references in steel and two-tone are widely available and represent outstanding value as mechanical dress-sport watches. The exposed screw design remains as distinctive and wearable today as it was at the dawn of aviation. DeMesy & Co. in Dallas has authenticated pre-owned Santos de Cartier watches since 1987.