iwc AQUATIMER CHRONOGRAPH Mode D'emploi page 36

Changing between different types of bracelet
Your IWC watch has a bracelet quick-change system* that
enables you to change the bracelet quickly and simply,
without the use of tools.
1
2
* The Aquatimer bracelet quick-change system has been developed by
IWC under a patent licence from Cartier.
To remove the bracelet, use your thumb
to push down the retaining lever (1)
on the underside of the horns.
While holding the lever down, slide the
connecting link out vertically from the
underside of the case (2).