The short answer: a fake IW371438 fails on three checks, and you can run all three without opening the watch. The subdials sit wrong or do not sweep, the dial printing is soft, and the caseback engraving is shallow or misspelled. The reference itself belongs to the IWC Portugieser Chronograph family, a two-register automatic chronograph with a wide, thin bezel and a dial that is mostly open space. That open space is why copies are easy to catch: there is nowhere to hide a sloppy detail.

Below are the checkpoints in the order a watchmaker would use them, with the signs that hold up and the signs that do not, plus a note on what each finding means for value and for service.

Case Shape, Crown and Pushers

The Portugieser case is a plain round shape with a narrow bezel and a domed crystal. Finishing on a real example is even, with a clean break between brushed and polished surfaces. Look at the crown and the two chronograph pushers: they should share one axis, sit at consistent height, and feel firm with no side play. Copies often show a crown that is too small, pushers that are too long, or a bezel wider than the dial needs.

• Hold up: case around 41 mm across, thin bezel, level crown and pusher heights, crisp lug edges.
• Warning: lugs that taper at an odd angle, or a bezel that crowds the dial.
• Warning: rough finishing inside the lugs, where a polishing wheel rarely reaches.

How to use it: photograph the case straight on and in profile. Copies survive the head-on shot and fall apart in the side view.

Dial Printing, Markers and Hands

Dial work is where the gap between real and fake is widest. On the genuine dial the maker's name under 12 is printed with sharp, even strokes, the applied numerals sit flat with clean edges, and the leaf-shaped hands are slim with a mirror polish and no burrs at the tips. Copies print thicker, and the lettering tends to bleed under magnification.

• Hold up: sharp printing, flat applied numerals, slim polished hands, even spacing around the track.
• Warning: fuzzy or doubled printing, numerals glued on at a tilt, hands that look stamped rather than finished.
• Warning: a dial surface with a plastic sheen or visible dust under the crystal.

How to use it: a 10x loupe and daylight beat any photograph. Check the same three letters in the maker's name every time.

Subdial Behavior and Chronograph Function

The classic two-register layout runs a chronograph minutes counter at 12 and running seconds at 6. Start the chronograph and watch the small hand at 12 move in small, steady steps. Reset it and it should snap back to zero at once. A copy with a cheap quartz or stripped automatic movement will tick, stutter, or drift off zero.

• Hold up: smooth sweep, instant reset to zero, no wobble in the small hands.
• Warning: a ticking subdial, a hand that misses zero, or a pusher that needs force.

How to use it: this is the one test you can run in a shop in under a minute, and it catches most fakes on its own.

Movement and Caseback

The 3714 generation of the Portugieser Chronograph is widely documented as using a Valjoux 7750 base movement finished and adjusted in Schaffhausen. Most examples of this generation have a closed caseback, engraved with the reference, the serial number and the maker's name. Engravings on a real watch are deep, even and readable at an angle.

• Hold up: deep engraving, consistent font, reference and serial that match the paperwork.
• Warning: laser-etched text that fades at an angle, mismatched reference codes, or a serial number shared by other listings online.

How to use it: write down the reference and serial and search them. Counterfeit batches reuse numbers, so a number that appears in many listings is a strong signal.

Why a Counterfeit IW371438 Is a Poor Deal

Counterfeit watches infringe trademarks, can be seized in transit, and cannot be serviced by the brand or by most independent watchmakers who stock genuine parts. Resale value is close to zero. Buyers who want the look of a Portugieser without the risk are better served by a genuine watch from a different brand at the same budget.

Who Should Use This Guide

Use it if you are buying secondhand, if you are selling and want to describe your watch with confidence, or if you have inherited a Portugieser and need to know what you own. Start with the subdial test, then the dial printing, then the caseback. If two of the three fail, stop and get a watchmaker's opinion before money changes hands.