Answer first
IW371634 sits in the IWC Portugieser Chronograph IW3716 series. That series runs a 41.0 mm case, a 13.1 mm height, a date window at 3 o'clock, subdials at 12 and 6, and IWC calibre 69355. Dial color, case metal, and strap for the 371634 number are not confirmed in this guide. Check them with an IWC dealer. A replica is a counterfeit watch, not an IWC, and it comes with no IWC warranty or service support.
Specs a copy has to match
- Case: 41.0 mm across, 13.1 mm thick, steel on most IW3716 numbers.
- Movement: calibre 69355, automatic, column wheel chronograph, 28,800 vph (4 Hz), 46-hour power reserve.
- Water resistance: 3 bar (30 m).
- Glass: sapphire at the front and the back, anti-reflective coating on both faces.
- Subdial at 12: elapsed minutes. Subdial at 6: running seconds.
- Date: window at 3 o'clock.
Measure the case with calipers. Most copies run 0.5 mm to 1.5 mm thicker than 13.1 mm. The extra space comes from a spacer ring that holds a smaller movement inside a larger case.
Movement tells
No replica carries a 69355. The common substitute is a 7750-pattern movement made in Asia. On a stock 7750 the subdial at 6 counts 12-hour totals, and running seconds sit at 9. The Portugieser dial puts running seconds at 6. Start the chronograph. The hand at 12 should sweep. The hand at 6 should keep running in one-second steps the whole time. If the hand at 6 stops while the chronograph runs, the layout is wrong.
Look at the rotor through the case back. IWC finishes the 69355 with Geneva stripes on the bridges and a skeletonized rotor with the IWC logo. Copies show plain brushed plates, a printed rotor, or shallow engraving. Some copies hide the movement behind a solid back. The genuine watch has a sapphire back.
Dial and printing
Check four areas:
- Applied numerals: polished metal edges, flat tops, no paint spill.
- Minute track: thin printed lines, even spacing, sharp ends.
- Text: "IWC" and "SCHAFFHAUSEN" in thin, even strokes. Copies show thick or uneven letters.
- Blue dials: genuine blue reads as a dark, flat tone with little color shift. Copies show purple in some light.
Price tiers
- Under $150: mineral glass, painted numerals, one dead subdial, wrong date font.
- $200 to $400: sapphire glass, printed dial, 7750 movement, case 1 mm to 2 mm too thick.
- $450 and up: closer case profile, working subdials, decorated movement, better steel finish.
Price sets the build level. It does not make a copy legal or authentic.
Checks before payment
- Ask for a caliper photo of the case at the 3 to 9 line.
- Ask for a video with the chronograph started, running, and reset.
- Ask for a photo of the case back and the movement.
- Ask for the date flip at midnight. A slow flip points to a low-grade movement.
- Compare the dial photo with an IWC photo at the same angle.
What is not confirmed
The dial color, case metal, and production years for reference IW371634 are not verified here. IWC lists specs for the IW3716 series, but not each number on one page. Treat any seller claim about the exact 371634 configuration as unconfirmed until you match it to an IWC source.
Legal status in the US
US Customs and Border Protection can seize counterfeit watches at import. Sale of a counterfeit in the US violates trademark law. No IWC service center will repair a replica with genuine parts.