The quickest way to spot a fake IW371790 is to study the dial printing and the caseback. Genuine IWC Portugieser chronographs carry sharp, raised lettering, registers that sit true on the vertical axis, and a caseback engraving or exhibition back that matches IWC's own reference data; counterfeit versions show soft edges, drifting subdials, and a generic movement that does not match the brand's finishing standards.

Because the IW371790 belongs to a clean, legible chronograph family, it is easy to copy in silhouette and hard to copy in detail. That gap between the overall look and the small details is where a fake IW371790 usually falls apart under a loupe or a phone camera.

Why the IW371790 Gets Counterfeited

Portugieser chronographs sell on design rather than on loud branding, which makes them attractive to counterfeiters. A copy can pass at arm's length because the case shape, the two-register layout and the slim bezel are simple geometry. The money in a genuine watch sits in the dial execution, the case finishing and the movement, and those are the three areas a counterfeit budget rarely reaches.

Dial Checkpoints

Printing and typography

• Genuine printing sits slightly above the dial surface and has crisp, unbroken edges. Fakes often look flat, fuzzy or slightly grey.
• Look at the brand name and the script under 12 o'clock. Letters should be evenly spaced, with consistent stroke weight; counterfeit dials show uneven kerning and thin spots.
• Check the small numerals and the minute track. On a fake, the track can drift closer to the edge on one side than the other.

Subdial alignment

• The two chronograph registers should sit on the same vertical line through the centre of the dial. A sideways shift of even a fraction of a millimetre is a warning sign.
• Inspect the snailing on the register surfaces. Genuine dials have fine concentric texture that catches light evenly; copies often use flat, printed rings.
• Hands inside the registers should reach the markers. Short or mis-set subdial hands are common on counterfeit examples.

Hands, markers and the date window

• Genuine hands have clean bevels and no burrs at the tips. Check the chronograph seconds hand for a straight counterweight.
• The date window should be cut cleanly, with sharp inner corners and no visible white edge from the dial blank underneath.
• Applied numerals should be seated flat, with no shadow gap on one side.

Case, Crown and Pushers

Case finishing is the second weak point. Genuine Portugieser cases mix brushed flanks with polished bevels, and the transition between the two is a defined line, not a soft blend. Run a fingernail along the lug edges: fakes often feel rounded where the genuine is sharp.

• The crown should be engraved with the brand's mark, with clean relief and no casting grain.
• Pushers should travel smoothly with a defined start and stop, and return without wobble.
• Lug holes, spring bar fit and caseback threads should feel precise rather than loose.

Caseback and Movement

If the watch has an exhibition back, the movement is the most reliable tell. Genuine IWC chronograph calibres show proper Geneva stripes, blued screws, engraved bridges and a signed rotor with the correct reference and serial markings. Counterfeit movements usually show stamped decoration, chrome-plated wheels, and a rotor screw instead of a signed medallion.

On a solid caseback, read the engraving. Genuine reference numbers, serial numbers and material stamps are cut deep with sharp shoulders. Laser-etched fakes look shallow and slightly brown at the edges under magnification. Cross-check the reference string against the brand's own published specifications rather than a marketplace listing.

Weight, Sound and Wrist Feel

A counterfeit chronograph tends to feel light in the hand and hollow when tapped. The rotor on a cheap copy spins freely and noisily in both directions; a genuine automatic winding system feels damped and quiet. Winding should be smooth with a steady resistance, not gritty or loose.

Box, Papers and Serial Numbers

• Compare the warranty card serial with the caseback serial. They should match, with the same font and the same depth of impression.
• Booklet print quality, paper stock and the cut of the inner cushion are all reproduced poorly on counterfeit sets.
• Ask for the original purchase date and dealer name, then verify that the reference existed in that configuration.

Price Sanity Check

If the asking price is far below the going rate for the reference in that condition, the watch is either damaged, stolen or fake. There is no scenario in which a genuine Portugieser chronograph sells for a fraction of its market value from an unknown seller with no service history.

If You Already Bought a Fake

Stop wearing it, photograph every angle and keep the listing, messages and payment record. Report the sale to the platform and your payment provider, and have a watchmaker confirm the finding in writing before you open a dispute. If the seller claims the watch is genuine, ask for a documented service record from an authorised centre.

Cheap Fakes vs. Premium 1:1 Replicas

It helps to separate two different products. A low-grade counterfeit is built to deceive a buyer into thinking it is genuine, and it is the version that shows soft printing and mismatched movements. A high-end 1:1 replica is sold openly as a replica, with a consistent dial layout, correct case proportions and a movement finished to a visibly higher standard.

If the look of the IW371790 is what you want, buy a replica that is described honestly as one, check the dial photos at full resolution, and confirm the return policy before paying. That approach keeps you out of the counterfeit market, where the watch is both a legal risk and a poor value.