Short answer
A fake IW371629 is a steel Portugieser Chronograph with a bicompax dial and a cheap chronograph module inside. Check four points: movement, dial print, case finishing, and the serial on the papers. One failure is enough to walk away.
What IW371629 refers to
IW371629 belongs to the IWC Portugieser Chronograph line, reference family 3716. That family runs a 41 mm steel case, a height near 13 mm, sapphire crystal, and 30 m of water resistance. The dial carries two counters: a 30-minute totalizer at 12 and small seconds at 6.
Reference numbers change with dial color, strap, and market. Confirm IW371629 against an IWC service record or an original invoice before you compare details. If the number appears in no official list, treat that as a flag.
Movement
The current Portugieser Chronograph uses calibre 69355, an in-house automatic with a column wheel and 46 hours of power reserve. Earlier ref. 3714 watches used calibre 79350, built on a Valjoux 7750 base. Fakes use a Chinese or Japanese chronograph module instead. Signs to look for: rotor engraving with soft edges, a chronograph seconds hand that stutters, pushers that feel gritty, and a date window pushed off center by the module. Ask the seller for a movement photo and a video of start, stop, and reset.
Dial and case
Read the printed text first. On the original, IWC and SCHAFFHAUSEN sit level with even stroke weight. Fakes show thicker letters, uneven spacing, or a smeared A. Applied numerals have polished edges and flat tops. Subdial rings are thin and concentric. The case has brushed flanks and polished bevels. A fake shows rounded edges and a polished caseback rim. Lug spacing is 20 mm. Crown engraving is deep and centered.
What fakes get wrong on this reference
- Case thickness. Fakes run 1 mm to 2 mm deeper to fit a cheap module.
- Subdial position. A 7750 base shifts the counters and adds a date at 3.
- Date font and aperture shape.
- Caseback text. Missing reference, wrong serial pattern, weak laser etch.
- Weight. Steel replicas sit 20 g to 40 g below the original.
Papers and price
A box and a card cost a faker little. Match the serial on the caseback against the card and the IWC service record. A used steel Portugieser Chronograph trades in the low thousands of US dollars. An offer far under that range is a fake or a stolen watch. No legitimate seller refuses an inspection at a service center at this price level.
Checklist before you pay
- Photograph the caseback serial and the reference stamp.
- Ask for the service record or invoice with a matching number.
- Rate the movement at 28,800 vph by video, if a display back is present.
- Time the chronograph for 10 minutes against a phone stopwatch.
- Weigh the watch head. Compare against published specs for the same dial version.
- Book an inspection at an authorized service center before funds move.
What this guide cannot confirm
IWC reference numbers for dial and strap variants are not published in one complete list. Verify IW371629 through IWC customer service or an invoice. Without that step, compare family traits only.