iwc AQUATIMER AUTOMATIC 2000 Operating Instructions Manual page 14

3
When attaching the bracelet, you must ensure that
the horns are securely engaged to prevent the bracelet
coming off your arm unintentionally.
To attach the bracelet, push down
the two sides of the horns vertically
towards the lower side of the case
and into the recesses (3) until you
hear and feel the retaining lever
engage.