Mechanism: 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.

Family Notes: The Rolex Day-Date was introduced in 1956. It soon became known as the "Rolex President". It was unofficially renamed after President Eisenhower became associated with this model watch. This association was made as the watch was known to have been worn by LBJ and shared a scandalous connection to JFK. Since then it has earned the vote of a diverse array of potentates, including Warren Buffett, Jay Z, and (fictional character) Tony Soprano. In 1977, Rolex started using the new (at the time) 3055 movement for the Day-Date/President line. As of 2018, the Day-Date 40 uses the 3255 movement.