Short answer: a fake IW371745 is a cosmetic copy of an IWC Portugieser Chronograph, and weak copies fail the same three tests every time: movement architecture, case finishing, and dial printing. If what you want is the Portugieser look, a pre-owned genuine reference or a no-logo homage gets you a serviceable movement and resale value for similar money. If you still plan to buy a replica, inspect those three areas first and treat every "1:1 Swiss made" claim as marketing until photos prove it.

What reference IW371745 is supposed to be

The number belongs to the Portugieser Chronograph line, IWC's steel chronograph with a twin-register dial measuring about 41 mm across. The layout puts elapsed chronograph minutes at 12 o'clock and running seconds at 6 o'clock, with slim leaf hands and a narrow bezel that makes the dial look larger than the case measurement suggests. Current generations run an in-house 69-series chronograph caliber with a column wheel, roughly 46 hours of power reserve, and a 4 Hz beat. Case thickness sits near 13 mm, and a sapphire caseback shows the movement. Any copy has to match that architecture, because the dial layout and the caseback view are the first two things a buyer sees.

What to check on a replica

Movement and dial layout

Subdial distance is the fastest tell. Copies built on generic chronograph movements often push the counters too far apart or too close to the center, which leaves the printing cramped or the date window misplaced. Ask for a video of the chronograph running: the minutes counter should jump cleanly once per minute, the reset should snap back to zero, and the pushers should feel firm rather than mushy.

Case finishing

Look at where brushed and polished surfaces meet. Genuine cases keep those transitions crisp around the lugs and the bezel edge. Cheap copies blur them, and the lug bevels look rounded. Check the crown engraving under magnification and inspect the pusher threads if they are screw-down.

Dial, hands, and crystal

Printing should stay sharp under a loupe, with no ink bleed on the minute track or the brand text. Applied numerals sit flush against the dial. Hands should be evenly finished with no tool marks, and a real anti-reflective coating makes the dial readable at an angle instead of turning it into a mirror.

Strap, clasp, and hardware

Stitching should be even and the leather should smell like leather. A stamped buckle with soft edges is common on replicas, and it is one of the easiest parts to replace if everything else passes.

Parameter bands worth measuring

• Case diameter: about 41 mm. A copy that measures 42.5 mm or 39 mm will wear wrong.
• Case thickness: about 13 mm. Much thinner points to a quartz or a modified three-hand movement.
• Lug width: about 20 mm. Measure before ordering a replacement strap.
• Beat rate: 28,800 vibrations per hour, or 8 ticks per second on a timing app. A 21,600 vph movement is a giveaway.
• Power reserve: roughly 46 hours. Test it by setting the watch down and checking after a day.

Pitfalls that cost buyers money

• "Swiss made" claims on a caseback that shows an Asian chronograph movement.
• Water resistance promises. A replica is only as sealed as its gaskets, and nobody pressure-tests it. Do not swim with one.
• No service path. Independent watchmakers often refuse counterfeit branded watches, and factory parts do not exist.
• No resale. A replica sells for a fraction of what you paid, if it sells at all.
• Seizure risk. Counterfeit trademarked goods can be stopped at the border, and your money is gone with the package.

Legal and ownership reality

In the United States, importing counterfeit goods is a trademark violation, and trafficking in them is a federal offense. That exposure reaches the buyer, not just the seller. Beyond the legal side, a replica is a watch that few shops will service, no authenticator will certify, and no collector will buy at a fair price.

Better routes to the Portugieser look

Three options beat a replica on every practical measure. A pre-owned genuine Portugieser Chronograph from an earlier generation costs less than a new one and holds value. A no-logo homage with a Seiko or Miyota chronograph movement gives you the same dial layout with honest service. A dress chronograph from a mid-tier brand gives you a real warranty and a real caseback to look at.

FAQ

Will a fake IW371745 fool a jeweler?

Not under a loupe. Case finishing, dial printing, and the movement behind a sapphire caseback are all readable in a few minutes.

Can I swim with a replica?

No. Treat any replica as splash resistant at best, even when the listing quotes 50 or 100 meters.

Are the most expensive replicas worth it?

Price tracks cosmetics, not durability. A higher tier copy buys cleaner dial printing and case polishing, and the movement is often the same generic chronograph caliber.

How do I confirm a watch is genuine?

Have the serial number verified by an authorized dealer or a watchmaker who works with IWC, and request the service history. Serial verification is the only reliable route.

What should I ask a seller before paying?

Request a video of the chronograph start, stop, and reset, a photo of the caseback, a photo of the movement, and the case diameter measured with calipers. A seller who avoids any of those is not worth the risk.