Top pick: a top-tier build of the fake IW371642 with a functional chronograph, a case that matches the original 41 mm Portugieser Chronograph profile, and dial printing at the right scale. Every option below is judged on four criteria: case and lug geometry, dial and hand finishing, chronograph movement behavior, and caseback engraving plus crystal quality. A build that fails two of those four reads as a fake from across a table, no matter how good the photographs look.

Why this reference is hard to copy

The IW371642 sits in the IWC Portugieser Chronograph line, a slim sapphire-and-steel design with two subdials, a date at 3, and a narrow bezel that leaves a large dial. Large dials are unforgiving. There is no wide bezel to absorb a logo that sits a fraction off center, and no busy texture to hide flat hands. Fakes of this reference live or die on small details, which is why the checks below matter more here than on a dive watch.

Criterion 1: Case and lug geometry

The Portugieser case is defined by its lugs. They are long, thin, and curve down toward the wrist instead of sitting flat. Replicas built on a generic case show thick lugs, a crown that sits too tall, or pushers out of proportion to the crown. Ask for a caliper photo of thickness measured across the crystal and the caseback, plus a straight profile shot. A case that looks a fraction tall in a photo will look wrong on the wrist, because the dial sits higher than it should under a shirt cuff.

Criterion 2: Dial, subdials and hands

Check the wordmark at 12, the chronograph text above the 6 o'clock register, and the date window. Original printing is crisp with consistent stroke weight. Budget replicas use a heavier font that looks slightly blobby under macro. Check subdial spacing too: both registers sit on the vertical axis with even margins to the bezel. Hands on the original are polished and faceted, so they show a bright face and a dark edge in the same frame. Flat painted hands are the fastest tell.

Criterion 3: The chronograph movement

The original runs an integrated chronograph with small seconds at 6 and a 30-minute counter at 12. A stock 7750 movement has its running seconds at 9, so any replica holding the correct 6/12 layout is using a reworked movement or a transfer module. That affects reliability, not just looks. Ask which approach the build uses, then ask for a video of start, stop, and reset. A healthy movement snaps back to zero without hesitation and the pushers feel firm rather than mushy.

Option A: Top-tier build

Pros

  • Case thickness and lug curve close to the original, so the watch sits correctly on the wrist
  • Working chronograph with correct subdial function and a date that changes cleanly
  • Sapphire crystal with anti-reflective coating on both faces, which is what gives the dial its depth
  • Caseback engraving deep enough to survive macro photography

Cons

  • Highest cost of the three tiers
  • Longer waiting period and more back-and-forth questions before shipping
  • Worth a service interval if you wear it daily

Best for: buyers who want one watch that holds up to a close look and who plan to wear it several days a week.

Option B: Mid-tier build

Pros

  • Correct dial layout and readable printing at arm's length
  • Solid case finishing for the money
  • Shorter lead time and easier to source in more dial variants

Cons

  • Movement module may be a lower grade, so the reset is less crisp
  • Anti-reflective coating single-sided or missing, which flattens the dial
  • Lug profile slightly thicker than the original
  • Caseback engraving shallow under raking light

Best for: occasional wear, rotation pieces, and buyers who want the look without the top-tier spend.

Option C: Budget build

Pros

  • Lowest entry point
  • Fine for photographs and desk duty
  • Parts and replacement straps are easy to find

Cons

  • Seconds hand stutter and a weak chronograph reset
  • Subdial spacing that drifts off the vertical axis
  • Painted hands with no facet
  • Water resistance claims you should not trust

Best for: someone testing whether they like the reference before committing to a better build.

Pre-purchase checklist

  1. Request a video of the chronograph running, stopped, and reset to zero.
  2. Request case thickness measured with calipers, crystal to caseback.
  3. Request macro shots of the dial print, the date window, and both subdials.
  4. Request a raking-light photo of the caseback engraving.
  5. Ask how the movement produces small seconds at 6, and whether it is reworked or module-driven.
  6. Confirm strap material, buckle engraving, and whether the clasp matches the case metal.

Work through those six items and you will separate the three tiers without needing to handle the watch. Buyers who skip the movement question are the ones who end up with a chronograph that resets to two seconds past zero.

Use-case recommendation

For daily wear and close inspection, take the top-tier build. For a rotation watch that leaves the box twice a month, the mid-tier build covers the dial-side details that people actually notice. For a first purchase or a gift where the recipient will not run the chronograph, the budget build is honest about what it is. Match the tier to how often the watch leaves the box, not to how good the listing photos look.