Quick Answer
A replica IW371491 is a copy of the IWC Portugieser Chronograph in its blue dial reference. A passable example matches four things: a case near 41 mm, a bi-compax dial with the 30 minute counter at 12 and the running seconds at 6, a 7750 based movement with a smooth sweep, and dial printing with the right weight. Check those four points before money changes hands and most of the junk on the market falls away.
Prerequisites
- Photos of the actual watch for sale, not catalog renders.
- The seller's stated movement type: Asian 7750, Swiss 7750, or quartz.
- A wrist shot for scale, since a 41 mm case wears large on a 6.5 inch wrist.
- A written return window of at least 7 days.
How to Vet a Replica IW371491
- Measure the case across the bezel, crown excluded, and confirm it lands between 40.5 mm and 41.5 mm.
- Check the thickness with calipers. Genuine IW371491 examples sit near 13 mm, while quartz copies come in under 11 mm and feel hollow in the hand.
- Look at the subdial position. The 30 minute counter belongs at 12 and the small seconds at 6, both centered on the vertical axis.
- Compare the dial text under a loupe. The IWC wordmark and SCHAFFHAUSEN line print thin and sharp, with even letter spacing.
- Request a video of the chronograph in use. Start, stop, and reset should snap, and the center hand should return to 12 without drift.
- Inspect the caseback engraving. Reference numbers and any foundation engraving should cut deep into the steel, not sit gray on the surface.
- Weigh the head on a kitchen scale. A steel case with a Swiss 7750 usually lands between 90 g and 110 g before the strap.
- Work the crown and pushers. A Swiss 7750 winds with light resistance, while a cheap 21 jewel copy grinds and wobbles.
Common Tells on Cheap IW371491 Copies
- Subdials pushed out to 3 and 9 because the builder reused a generic chronograph dial.
- Printed text that bleeds or fuzzes at 5x magnification.
- A chronograph seconds hand that rests short of 12 after reset.
- Rotor noise audible from a foot away.
- Sapphire with a blue or purple tint when tilted toward a light source.
Movement Tiers and What They Cost You
Quartz examples keep time and stop there. The chronograph hand ticks once per second, the pushers feel dead, and the case is thin because nothing sits inside it. The Asian 7750 is the middle tier: automatic, sweeping, and fine for daily wear, though it can run fast and the rotor is loud. A Swiss 7750 or a decorated clone of the 79350 is the top tier, and it is the only version worth buying if you plan to keep the watch for years. Ask which one is inside, then ask again in writing. Sellers who dodge the question usually have a quartz build in the box.
Before You Pay
Get the serial region and the dial variant confirmed, since the IW371491 came with a blue sunburst finish and later runs differ in shade. Confirm the strap material and the buckle stamping. Pay with a method that can be reversed. Once the watch lands, repeat the case measurement and the chronograph test on day one, while the return window is still open.