IWC Schaffhausen AQUATIMER AUTOMATIC 2000 Mode D'emploi page 26

Water-resistance
In order to ensure its perfect function, you must have
your watch inspected by an IWC service point at least
once a year. An inspection must also be carried out after
the watch has suffered abnormal stresses (shock).
If these inspections are not carried out as stipulated,
or if the watch is opened by unauthorized persons,
IWC will decline any guarantee or liability claims.
Recommendation: Your IWC Official Agent must
perform a new water-resistance test every time your
IWC watch is opened and serviced.