IWC reference IW371787 does not appear in public IWC catalogs or in the main reference databases for the Portugieser line. The digits that follow the base number are case, dial, and strap codes. No published list we checked shows 87 in that slot. If a watch is offered with that number, verify the paperwork first, not last.
What the 3717 prefix covers
Reference prefixes in this range map to the Portugieser Chronograph. Public listings show 3714 and 3716 examples. The 3714 generation measures 40.9 mm and runs caliber 79350, a Valjoux 7750 base. The 3716 generation measures about 41.1 mm and runs caliber 69355, an automatic column-wheel chronograph with a 46-hour power reserve and a 4 Hz beat rate. For 371787, IWC is the source to use.
Case and dial checks
- Case width: a steel Portugieser Chronograph sits near 41 mm. A 43 mm or 39 mm case under this reference is wrong.
- Dial: applied Arabic numerals, printed minute track, two subdials at 12 and 6.
- Date window: rectangular, at 3 o'clock, with a date disc that matches the dial color. A white disc on a blue or black dial is a common replica tell.
- Crown: signed with the IWC letters or the fish, depending on production year. Check the engraving depth.
- Crystal: sapphire with anti-reflective coating on most variants. Acrylic is wrong for this model.
Movement
Ask for a photo of the movement through the display back. Caliber 69355 has a column wheel, a 46-hour power reserve, and a 28,800 vph beat rate. Replica cases in this family often hide a stock 7750 clone. That clone also beats at 28,800 vph, but it lacks the column wheel and shows a different bridge layout. A watchmaker can confirm the caliber marking in about ten minutes.
Serial, papers, price
IWC stamps the case number and movement number on the caseback and records them in the papers. A watch bought from an authorized dealer has a warranty card dated at purchase. Box, card, and hangtag sets exist for replicas and prove little on their own. Secondary-market prices for a steel Portugieser Chronograph run from the low four figures to near five figures in USD, based on age and condition. A new-in-box IW371787 offered far under that range is a flag.
Steps to verify
- Search the full reference on IWC's site, or call an IWC boutique and read them the number.
- Ask the seller for the case number, movement number, and purchase date.
- Request clear photos of the caseback engraving and the movement.
- Have a watchmaker open the case and confirm the caliber.
- Measure the case width against the spec for that variant.
What we could not confirm
We found no public IWC catalog entry, press release, or reference database listing for IW371787. The number may be a dealer code, a typo, or an unlisted limited run. IWC can settle it.