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Movement tier: unclassified
Large case: suits wrists 7 in+ (18 cm+)
43.5 mm case. A bold, statement-size wear. Best suited to larger wrists where the case sits flush.
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Authentication
Test the regatta countdown timer; it must set correctly for both 5-minute and 10-minute pre-start sequences before purchase.
Known issues in the market
- The regatta countdown adds complexity beyond a standard chronograph; service is specific to Cal. 89361 and requires IWC or IWC-certified expertise.
- The pusher at 10 o clock activates the countdown; verify it operates cleanly and does not bind.
| Area | What to check | What is correct | Red flag |
|---|---|---|---|
| case | Regatta timer pusher at 10 o clock | Pusher at 10 o clock activates the regatta countdown; operates cleanly with no binding | Pusher at 10 o clock binding or failing to activate countdown; may indicate service need |
| dial | Regatta timer countdown display | Countdown function sets for 5-minute and 10-minute sequences correctly; countdown display advances cleanly | Countdown not advancing correctly; timer not resetting to the correct interval |
| caseback | Cal. 89361 movement | Cal. 89361 confirmed through caseback; regatta complication architecture visible | Any caliber other than 89361; standard chronograph without regatta mechanism |
Common legitimate replacements
- Original IWC Portugieser strap or bracelet; factory replacements are standard.
Expert resources: IWC Portugieser Yacht Club Chronograph IW390503 product documentation. IWC Cal. 89361 technical sheet.
Authentication guide
Last reviewed June 2026
The IW390503 Portugieser Yacht Club Chronograph uses a flyback movement (Cal. 89361) in a 45.4mm steel case with a rubber strap and push-button deployant. The larger diameter and rubber strap give it a more sports-oriented character than the standard Portugieser Chronograph.





