Short answer
IW371765 is an IWC reference in the Portugieser Chronograph family. The watch carries a steel case of about 41 mm, a two-register dial, and an in-house IWC caliber 69355. Counterfeits exist, but they are far less common than fake Rolex watches. Most copies run an Asian 7750 pattern movement or a quartz module and sell for $200 to $700. No counterfeit holds a real IWC 69355. That is the first check.
What the reference is
IWC sorts references by family. Numbers in the IW37 block belong to the Portugieser line. Current chronographs in that line measure about 41 mm across and about 13 mm thick. Sapphire covers the dial. A sapphire display back shows the movement. Water resistance is rated at 3 bar. The dial holds a chronograph minutes counter at 12 o'clock, running seconds at 6 o'clock, a date window at 3 o'clock, and a printed minute track on the flange.
IWC changes references and movements over time. IWC does not publish a public archive of every number. Confirm the exact variant with IWC or an authorized dealer. If a listing shows specs that do not match IWC's own product page, treat the listing as suspect.
Movement checks
Ask the seller for a photo of the running movement through the caseback.
- Balance rate: caliber 69355 runs at 4 Hz. The chronograph seconds hand sweeps in 8 steps per second. A quartz fake ticks once per second.
- Subdial count: the IWC layout has two registers. A Valjoux 7750 base puts a third hand at 9 o'clock. Three registers means the dial is not the IWC layout.
- Engraving: real movements carry IWC markings on the rotor and bridges. Copies show flat, shallow stamping or no stamping.
Power reserve is a weak test. The 69355 runs about 46 hours, and a 7750 copy runs in a similar range.
Case and dial checks
- Caseback: the reference number and case serial are engraved into the metal. Many fakes laser etch a gray, flat mark with a wider font.
- Crystal: front and back are sapphire. A mineral glass fake shows scratches after normal wear.
- Pushers: start, stop, and reset feel firm, and the reset snaps back. Copies with a 7750 base often reset with a lag or a soft click.
- Bracelet and strap: end links fit with no rattle. Hollow links on a fake flex and clatter.
- Numbers: the reference and case number on the caseback must match the paperwork. Ask IWC customer service to confirm the case number.
Paperwork and price
A steel Portugieser Chronograph sells above $7,000 new. A watch listed as an IW371765 for $600 with a full box and papers is a counterfeit. Real papers show a reference number, a case number, and a dealer stamp. Blank cards or reprinted cards are a warning sign.
What sellers offer
Replica listings use terms such as 1:1, Swiss made, and super clone. The movement inside is an Asian 7750, a Seagull ST19, or a quartz module. IWC does not sell the 69355 as a loose part at low cost, so a sub-$1,000 watch cannot contain one. Photos in these listings are often of a genuine watch, not the item shipped.
Legal note for US buyers
Importing counterfeit watches into the United States is barred under 19 U.S.C. 1526. CBP can seize and destroy the shipment. Trafficking in counterfeit goods violates 18 U.S.C. 2320. Selling a fake as a genuine IWC is fraud under state and federal law.
Bottom line
Check the movement first, the caseback engraving second, and the papers third. If the seller will not send a photo of the running movement, walk away.