The Rolex Superlative Chronometer certification COSC has been a mainstay for Rolex since the mid 1950's.  Rolex guarantees your watch is accurate to -2/+2 seconds per day, after casing. The COSC requires only a -4/+6 per day accuracy.  Even Omega's Master Certification requires a 0/+5 accuracy. 

Rolex considers accuracy the utmost importance to its timepieces and strives to achieve near perfection in its craft - demanding of itself higher standards than the competition.  

Rolex runs each of its timepieces through a battery of tests internally.  Besides precision, Rolex tests waterproofness, power reserve, and self-winding.  Once completed, these movements are sent out to COSC for an official independent certification, before casing.  

The Green Seal that comes with a Rolex includes a guarantee and warrantee of 5 years.  The green seal means that Rolex has spent tremendous amount of money and time to ensure each timepiece is accurate and reliable.  On many of the timepieces Rolex proudly displays the Superlative Chronometer wording on  the dial itself.  

The President's Day Date from Rolex has two inner wheels to contend with.  Not only does it have the date wheel but also the day of the week wheel to manage.  The Day Date with no quickset would be very time consuming to push through the date and day sets in order to get to the appropriate calendar and week day views.

However, the quickset features allowed the date to be adjusted quickly.  Yet, with the Presidential Day Date, this was not enough.  There had to be a separation between the Day of the Week wheel and the Calendar month wheel in order to have the power to easily set either the week or the month independently.  So, Rolex came up with a solution - the Double Quickset Feature.

Rolex has had an enormous set of inventions and enhancements developed for their timepieces over the years.  In 1972 Rolex developed the hack.

The issue that early Rolex calibers would lose seconds when pulling out the crown and setting the time (hour and minutes hands).  With hacking technology, the seconds hand can be stopped and adjusted and synched to another source.  This feature increases accuracy.  Since the seconds don't stop in non-hacking timepieces, you could never get an exact synchronized time with any resource.  The closest you could get would be to the minute.

There are many instances when having hacking and to the second accuracy is essential.  Military operations is clearly the most obvious.  Hacking was not uncommon in some timepieces during the war to coordinate bombing runs, but it wasn't until 1972 when Rolex adopted the technique.



With the release of the caliber 1570 in 1972, it was now possible to stop the sweeping seconds hand by pulling out the watch crown, activating a hacking lever that interrupted the balance wheel and simplifying the act of setting the watch accurately.

The enhancement is a small channel machined into the caliber plate.  It is fitted with a spring tension which is activated straight through to a thin metal bar located between the winding pinion and  touching the balance wheel.  It works similar to a hand break on a car so as you pull out the crown the seconds movement can stop and be adjusted precisely.