The top pick for a fake IW371766 is a steel Portuguese Chronograph at roughly 40.9 mm with two subdials stacked on the vertical axis, a sweep seconds hand at 6 o'clock, a 30 minute counter at 12 o'clock, and no date window. The criteria below are the ones that decide whether a first copy reads correct on the wrist: case dimensions, dial print and hands, chronograph behavior, crystal and caseback, and strap finishing. Everything else is detail you notice only under a loupe.

What the search "fake IW371766" actually means

IW371766 is an IWC reference inside the Portuguese Chronograph family. The first characters identify the model line and the trailing digits encode dial and strap combinations, so several watches share the same case under different suffixes. Searches for a fake IW371766 almost always point to a replica of that watch rather than a counterfeit being resold as genuine. The reference appeals to buyers because the dial is sparse enough to photograph well and the case wears closer to a dress watch than a sports chronograph.

Treat "fake" as a quality question, not a yes or no. Replicas of this reference arrive in tiers that differ in dimensions, dial printing, and how the chronograph actually behaves when you press the pushers.

Top pick: steel case, correct profile, 7750 based movement

The version worth chasing uses the original case proportions, a domed sapphire or good mineral crystal, and a chronograph built on the Valjoux 7750 architecture or a close clone of it. That combination gives you the right subdial positions, a running seconds hand that sweeps rather than ticks, and pushers with a defined start, stop, and reset sequence.

Pros

  • Subdials land where the original puts them, so the dial reads correct at arm's length.
  • Chronograph functions in the right order instead of being a decorative pusher.
  • Case thickness stays close to the genuine profile and slides under a cuff.

Cons

  • Costs more than quartz driven replicas with printed subdials.
  • Automatic chronographs need service eventually, and not every seller can do it.
  • Rotor noise is audible on cheaper 7750 clones.

Use case: buy this tier if you plan to wear the watch often and want the chronograph to work when someone asks about it.

Criterion 1: Case size and profile

The genuine Portuguese Chronograph sits just under 41 mm across with a relatively slim mid case. Replicas that stretch to 42 or 43 mm lose the proportions and wear large on a 6.5 inch wrist.

Pros of a correctly sized case

  • Lugs curve down and sit flush on the wrist.
  • Strap width matches the original, so aftermarket straps fit.
  • Crown and pushers sit at the right height relative to the caseband.

Cons of chasing exact dimensions

  • Fewer sellers list measured dimensions, so you have to ask.
  • Sub millimeter differences are hard to verify from photos alone.
  • Smaller cases sometimes carry thicker movements and sit tall.

Use case: a smaller wrist should prioritize measured dimensions over dial color, since an oversized case is the first thing people notice.

Criterion 2: Dial layout, print, and hands

This is where most replicas fail. The original uses leaf shaped hands, applied Arabic numerals, and a clean outer track. Look for a printed minute track that stays crisp under magnification, subdial rings that are concentric, and no date aperture cut into the dial.

Pros of a well finished dial

  • Applied numerals cast a real shadow instead of sitting flat.
  • Hands reach the correct markers at each hour.
  • Text weight and spacing hold up in photos.

Cons and common faults

  • Flat printed numerals on cheaper builds.
  • Subdial hands that sit too short or too long.
  • Logo print that looks heavy or smeared.

Use case: if you buy one thing well, buy the dial. It is the part of the watch other people actually see.

Criterion 3: Chronograph behavior

Press the top pusher. The center seconds hand should start with a light click, not a grind. Press it again and the hand should stop cleanly. The bottom pusher should snap everything back to zero in one motion.

Pros of a working chronograph

  • Confirms the watch uses a real chronograph movement rather than a decorated plate.
  • Reset returns to twelve without drift.
  • Running seconds at 6 o'clock sweeps smoothly.

Cons

  • Modular chronographs add thickness and cost.
  • Cheap clones can lose reset alignment over time.
  • Leaving the chronograph running drains power reserve.

Use case: skip any replica where the pushers are fixed or the subdials are painted on, even if the dial looks good.

Criterion 4: Crystal, caseback, and water resistance

A domed crystal with a subtle edge distortion reads closer to the original than a flat pane. On the back, engraving should be shallow and even, and any claimed water resistance should be treated as splash resistance only unless the seller states the gasket spec.

Pros

  • Sapphire resists the scratches that ruin a daily wearer.
  • Clean caseback engraving signals a better finished case.
  • A screw down back is easier to service later.

Cons

  • Mineral crystal picks up hairline scratches within months.
  • Deep engraving and heavy laser marking look wrong in daylight.
  • Water resistance claims on replicas rarely survive a pressure test.

Use case: keep any replica away from swimming and showers regardless of what the listing says.

Criterion 5: Strap, clasp, and wear

Alligator grained leather with a deployant clasp is the usual pairing. Check stitch density, edge paint, and whether the clasp closes with a firm click.

Pros

  • A good strap makes an average case look better.
  • Standard lug widths let you swap in a better strap later.
  • A working deployant saves the leather from creasing.

Cons

  • Stock straps on budget replicas stiffen and crack.
  • Clasps with sharp edges catch on sleeves.
  • Branded buckles invite scrutiny you may not want.

Use case: budget for a replacement strap. It is the cheapest upgrade with the largest visible effect.

Legal and practical note

Selling a counterfeit as a genuine watch is illegal in the United States and most other markets, and the pieces discussed here are replica grade items sold as replicas. They are not investment pieces and hold no resale value. If authenticity matters to you, buy from an authorized dealer and keep the paperwork.

Which tier fits which buyer

Buy the automatic tier if the chronograph needs to work and the watch will be worn weekly. Buy the mid tier with a correct dial and a quartz or basic automatic movement if you want the look without service costs. Skip anything with painted subdials or an oversized case, since those faults are visible from a distance and no strap upgrade will hide them.