The single most important thing to check on a replica IW371787 is dial geometry, not the logo. The chronograph counters on this reference sit at 12 and 6, and the distance between them, the size and position of the date window, and the length of the hands decide whether the watch reads as convincing on the wrist. A sharp logo on a dial with counters set too far apart is still an obvious copy. Settle the proportions first, then judge the finishing.
What to look for
Case proportions and lug profile
The Portugieser chronograph family has moved between roughly 40.9 mm and 42 mm across generations, so ask the seller for caliper photos of the actual piece rather than trusting a listing description. Genuine cases are slim and stepped, with lugs that curve down and hug the wrist. Replicas commonly run one to two millimeters thicker, and the extra height shows up in profile shots. Check lug tip shape, the polish line between brushed and polished surfaces, and whether the crown and pushers sit flush with the case band.
Dial printing, hands and crystal
Look for a crisp railway track minute ring, applied numerals with clean edges, and feuille hands that taper to a fine point. Printing that looks thick or slightly fuzzy under magnification is a giveaway. Subdial spacing is the detail most copies get wrong, so compare a straight-on dial photo with a reference photo at the same angle. Anti-reflective coating should be subtle; a strong blue or purple wash usually means a cheap coating. The date aperture should be framed and centered, not stamped through the dial.
Movement and caseback
Most replicas in this size run a modified Valjoux 7750 layout or a Chinese chronograph movement, which pushes the subdials and date to positions the original never used. Pusher feel tells you a lot: a column-wheel chronograph starts and stops with a light, separate click, while a cam-actuated copy feels heavier and less defined. Reset should snap back to zero instantly. On a display caseback, decoration such as Geneva stripes and a signed rotor can hide a rough gear train, so ask for a video of the chronograph running rather than a still photo of the movement.
Strap, clasp and hardware
Stitching pitch, lining material and buckle engraving separate the tiers quickly. Embossed alligator pattern on a stiff leather strap is common at the low end. Spring bars should be thick and seated properly, and the buckle should not feel hollow or light in the hand.
Parameter bands
- Entry tier: stamped or poorly polished dial furniture, weak or absent anti-reflective coating, subdial spacing noticeably off, chronograph that stutters on reset, thin strap.
- Mid tier: sapphire crystal, sharper printing, better case finishing, smoother pusher action, decorated movement, hand-stitched strap with correct hardware.
- Top tier: case proportions within a fraction of a millimeter of the published spec, correct dial furniture and date position, well-finished movement with a clean chronograph action, accurate buckle and strap details.
Common pitfalls
- Buying from studio photos alone. Request a wrist shot in daylight and a straight-on dial shot.
- Treating a decorated rotor as proof of a good movement. It is cosmetic.
- Ignoring subdial spacing because the case looks right.
- Believing water resistance claims. Gaskets on replicas are rarely pressure tested, so do not swim with one.
- Assuming service support. IWC will not touch a counterfeit, and many independent watchmakers will decline the work or struggle to source parts.
- Overlooking plated finishes on two-tone or gold-colored versions, where the plating wears through at the crown and lugs.
FAQ
Is the IW371787 a real IWC reference?
Yes. The number follows IWC's reference format for the Portugieser chronograph line, which is why replica listings use it as a shorthand for the case, dial layout and strap combination of that generation.
What movement should I expect inside a replica?
Most are 7750-derived or a Chinese chronograph caliber with a modular layout. Expect a unidirectional winding feel, more rotor noise than the original, and a chronograph action that is functional but less refined.
Does the date window position matter that much?
It does, because it is one of the first things an experienced eye catches. A date placed too close to the center or too high in the aperture breaks the symmetry of the dial.
How do I compare two sellers fairly?
Ask both for the same set of images: straight-on dial, case profile, caseback, buckle, and a short video showing the chronograph start, stop and reset. Identical requests make differences between the pieces easy to see.