Rolex 1556

History: The 1556 was specifically built for the Day-Date "President" family of watches. The 1556 was released in 1965 as the successor to the 1555 movement. Ostensibly identical, the only major difference between the two movements was a considerable rise in balance frequency. The later caliber followed the example set by the rest of the 1500 series and saw its rate increased to 19,800 VPH. As well as a marginal improvement in accuracy, the higher beat gave the mechanism an added imperviousness to shocks.

The 1556 was the last of the 1500 series to power the Day-Date. Rolex deemed that this flagship watch line needed a hacking feature and the 1500 series was not made to hack. Hence, this movement does not have a hacking capability. The 1556 was replaced by the 3055.

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