Answer
IW371736 is an IWC reference number. Listings that use it describe a Portugieser Chronograph: round steel case, two registers, leather strap. A fake IW371736 is a counterfeit. The caseback carries the reference number and the IWC name. The watch was not made by IWC. Genuine examples sell near $8,000. Copies sell from $80 to $700.
What the genuine watch does
- Case: stainless steel, 40.9 mm on older 3714 refs, 41 mm on current refs.
- Movement: calibre 69355 on current refs, an in-house column-wheel chronograph with 46 hours of power reserve. Older refs use calibre 79350, a modified Valjoux 7750.
- Crystal: sapphire with anti-reflective coating on both faces.
- Water resistance: 30 m on most refs. Not a dive rating.
- Retail: about $7,900 to $8,400 for a new steel model on a strap.
Checks that separate real from fake
- Subdial positions. Copy cases often take a 7750 layout, which puts the registers off the vertical center line or at the wrong depth.
- Pusher feel. Genuine pushers have a short, firm travel. Start, stop, reset. A 7750 or Seagull ST19 copy feels gritty, and the reset snaps.
- Dial print. The IWC logo, the word SCHAFFHAUSEN, and the model script are crisp and level. Fakes show thick strokes, uneven spacing, and soft serifs under a loupe.
- Numerals and hands. Applied numerals sit at one height and are polished. Fake numerals lift at the edges or sit in visible glue.
- Caseback engraving. Reference, case number, and material marks are cut deep. Laser-etched fakes look shallow and gray.
- Serial number. Ask IWC or an authorized dealer to confirm the case number. Fake serials repeat across many copies from the same factory.
- Movement finish. A watchmaker can open the back in minutes. A stock 7750 shows a plain rotor and no IWC marking under the balance.
- Weight. A steel Portugieser on a leather strap weighs about 80 g to 100 g. Many copies come in lighter because of a thin case.
- Price. Pre-owned genuine examples trade from $5,000 to $7,000. Any listing under $1,500 is a fake.
Limits of a photo check
Photos hide case thickness, movement finish, and engraving depth. A dial that looks correct in a listing photo can sit on a 7750 copy. Buy with a return window, or meet the seller at a watchmaker and pay for an inspection.
Law in the United States
Counterfeit watches are illegal to sell and to import. 18 U.S.C. 2320 covers trafficking in counterfeit goods. U.S. Customs and Border Protection seizes shipments that carry fake trademarks. A buyer can lose the watch and the money.
What is not known
IWC does not publish a full catalog of every reference on its public site. I could not verify a spec sheet for IW371736 by number alone. Confirm case size, calibre, and production years with IWC before you rely on any single listing.