Rolex 3156

History: Self-winding movement, bi-directional winding, 28,800 A/h, 31 jewels, Glucydur balance wheel with Microstella weight screws, newly developed Parachrom blue Breguet hairspring, newly developed Paraflex Antichock system, date and day of week indication.

Designed for and introduced with the 2008 Day-Date II model. The Day-Date II is equipped with the calibre 3156, a selfwinding mechanical movement entirely designed and manufactured by Rolex. It features a day and date calendar disc mechanism. The 3156 is fitted with a Parachrom hairspring and high performance Paraflex shock absorbers developed by Rolex, offering greater resistance to shocks and to extreme conditions. Like all Rolex Perpetual movements, the 3156 is a certified Swiss chronometer, a designation reserved for high-precision watches that have successfully passed the Swiss Official Chronometer Testing Institute (COSC) tests. Its architecture, in common with all Oyster watch movements, makes it singularly reliable.

Manufacturer: Rolex SA (/ˈroʊlɛks/) is a Swiss luxury watchmaker. The company and its subsidiary Montres Tudor SA design, manufacture, distribute and service wristwatches sold under the Rolex and Tudor brands. Founded by Hans Wilsdorf and Alfred Davis in London, England in 1905 as Wilsdorf and Davis, Rolex moved its base of operations to Geneva, Switzerland in 1919. Forbes ranked Rolex 64th on its 2016 list of the world's most powerful global brands.[Rolex is the largest single high end watch brand. The company is owned by the Hans Wilsdorf Foundation, a private family trust.

Alfred Davis and his brother-in-law Hans Wilsdorf founded Wilsdorf and Davis, the company that would eventually become Rolex SA, in London, England in 1905. Wilsdorf and Davis' main commercial activity at the time involved importing Hermann Aegler's Swiss movements to England and placing them in high-quality watch cases made by Dennison and others. These early wristwatches were sold to jewellers, who then put their own names on the dial. The earliest watches from Wilsdorf and Davis were usually hallmarked "W&D" inside the caseback.

From Wikipedia