The top pick for a replica IW371787 is a Swiss-movement Portofino-style chronograph with a steel case, a correctly spaced two-subdial dial and a signed strap with a deployant clasp. Four criteria decide whether a copy is worth wearing: the movement inside, the dial layout and printing, the case finish, and the strap and clasp hardware. Run the list below against any listing before you commit.
What the IW371787 reference points to
Listings that use the IW371787 number usually describe a steel chronograph from IWC's Portofino family: round case, narrow bezel, applied indices, a day and date window at 3 o'clock, and a bicompax dial with chronograph minutes at 12 and running seconds at 6. Check the dial photo against a reference image first. A subdial in the wrong position, or a date window that sits too close to the rehaut, is the fastest tell on a wrist.
- Confirm the case diameter matches the reference you are copying, not a generic 42 mm mould.
- Look for a stepped, polished bezel and brushed case flanks, since the contrast is what reads as expensive.
- Ask for a straight-on dial shot and a wrist shot. Angled renders hide printing flaws.
Movement: Swiss chronograph or quartz
The movement is where most of the money goes. A Swiss or Swiss-style automatic chronograph gives you a sweeping seconds hand, a working chronograph with a crisp reset, and a case back thick enough to sit correctly on the wrist. A quartz build is thinner, cheaper to service and more accurate day to day, but the ticking seconds hand and the flat pusher feel are obvious on a watch with an exhibition back.
Automatic chronograph
- Pros: sweeping seconds, correct pusher feel, correct case thickness, easier to pass as the real thing.
- Cons: heavier, needs a service interval, and a poorly finished rotor is visible through a display back.
Best for: someone who wears the watch daily and wants the weight and hand feel to match the reference.
Quartz chronograph
- Pros: lower cost, keeps time without winding, thin profile, few moving parts to fail.
- Cons: ticking seconds hand, hollow pusher action, and a case back that often sits too flat.
Best for: a first replica, a gift, or a watch that will sit in a drawer most weeks.
Dial, case and finish checks
Ask the seller for these specific photos, then compare them side by side with the reference.
- Dial printing: the brand text and the model line should be crisp, level and the same weight. Fuzzy printing is the first thing a jeweller notices.
- Indices: applied markers should sit flat, cast a small shadow and line up with the minute track.
- Hands: the hour and minute hands should reach the correct point on the track; a short hour hand is a common fault.
- Crystal: sapphire with an anti-reflective coating on both faces reads far closer to the original than mineral glass.
- Case back: engraving depth, spacing and font weight should match the reference, not a generic stamp.
Strap, clasp and water resistance
A cheap strap ruins a good case. Look for a leather strap with stitched edges, a soft inner lining and a signed deployant clasp that closes with a firm click. Ask what the water resistance rating actually is, then treat it as decorative. A chronograph with push-in pushers should never see a swimming pool, whatever the listing claims.
- Pros of a leather strap build: correct period look, comfortable on a small wrist, easy to swap.
- Cons: leather shows wear fast, and a weak clasp is the part most likely to fail first.
Best for: office and evening wear, where the watch is seen up close but not exposed to water or impact.
Where replica IW371787 builds fall short
Case profile is the usual weak point. Genuine Portofino cases have a soft curve into the lugs that most copies flatten. Movement finishing is the second gap: a display back exposes a rotor and bridges that no replica factory finishes to the same standard. Third is long-term parts support. Buy from a seller who stocks or can source a replacement movement, because a broken chronograph module is often a total loss.
Use-case recommendation
For daily wear and a convincing wrist presence, choose the automatic chronograph with a sapphire crystal and a signed deployant clasp. For occasional wear or a lower budget, the quartz version is the sensible pick, as long as you accept the ticking seconds hand. In both cases, spend your money on the dial and the case finish first, because those are the parts other people actually see.