Short answer
IW376091 follows the IWC reference format: the letters IW plus six digits. Sellers list watches under this number on marketplaces. Counterfeit watches print the same number on the caseback. The reference alone proves nothing. A correct reference does not mean the dial, case and movement belong together.
No public IWC document states which model carries IW376091. Ask IWC customer service or an authorized dealer to confirm the case material, dial and calibre for this number. A seller's description is not confirmation.
What the reference does and does not tell you
IWC assigns references by family and production run. Numbers close to each other often share a case and a movement. The reference identifies a model line, not a single watch. The serial number identifies the single watch. Both numbers must match the paperwork.
Caseback
IWC engraves casebacks with a cutter. Characters have depth. Run a fingernail across the reference and serial. Fakes use shallow laser marks with a flat bottom.
The serial is one number tied to one watch. Sellers reuse the same serial photo across listings. Search the serial against the reference before you pay.
Movement
Ask for a photo of the movement before purchase. Many IWC chronographs of the 2000s run the calibre 79320, a modified Valjoux 7750. Clones of that base show flat polishing on the rotor, wrong font on the rotor engraving, and a shock spring of the wrong shape. Have a watchmaker open the case and read the calibre number.
Dial and hands
Check the date wheel font and the date window bevel. The 7750 base fixes subdial spacing. A fake built on a different base shows wider or narrower spacing than catalog photos of the same reference. Index edges are sharp. Lume sits inside the marker, not over the edge.
Crown and pushers
Crown threads engage in less than one full turn on many fakes. Pushers return with a crisp click on a real chronograph. Check the crown logo for clean edges and correct letter spacing.
Crystal
The crystal is sapphire with anti-reflective coating on both faces. It shows a faint blue or purple tint at an angle. Mineral glass scratches and shows no coating tint.
Case and bracelet
Brushed and polished surfaces meet at a hard edge on a real case. Put the watch on a scale and compare the result with the same reference. Hollow links and plated cases show up in the number.
Paperwork
Check the warranty card, booklet and box. The serial on the card matches the caseback. The card carries a dealer stamp and a sale date. IWC does not issue blank cards.
Price signals
A genuine IWC chronograph sells for thousands of dollars on the secondary market. A listing far under that range is a fake or a parts watch. Sellers who ask for payment outside an escrow platform are a red flag.
Steps before you buy
- Read the reference and serial from a caseback photo.
- Ask IWC or a dealer to confirm the pair.
- Request photos of the movement, caseback, dial and clasp.
- Compare subdial spacing and date font with catalog photos of the same reference.
- Have a watchmaker open the case and read the calibre number.
- Pay with a method that allows a chargeback.