The short answer: a fake IW371785 usually survives a glance and fails a loupe. The silhouette is easy to copy. The things that give it away are movement finishing, subdial spacing and depth, the crispness of the dial print, and how the chronograph pushers feel under your thumb. Genuine Portugieser chronographs start and reset with a clean mechanical snap. Most fakes feel spongy, and the reset sometimes hangs for half a second.
Check the movement first
Flip the watch over. The genuine IW371785 family runs an IWC-calibrated chronograph movement, and the decoration is the tell. Look for even Cotes de Geneve stripes, tight perlage on the mainplate, blued screws seated flush, and a rotor engraving with sharp edges. Fakes often use sticker-thin decoration, wavy stripes, and rotor text that looks painted rather than engraved. If the caseback is solid, that alone is worth a question. A seller who cannot show the movement or explain the caliber is a seller to walk away from.
Dial print and subdial layout
This is where replicas slip most often. On the genuine dial, the applied numerals sit slightly above the surface with crisp, polished edges. The printing is flat and dense, with no fuzzy borders under magnification. Subdials should be perfectly spaced and slightly recessed, with fine concentric snailing that catches light at an angle. Fakes tend to print the subdials flat, misalign the 12 and 6 counters by a hair, or use a date window that sits a fraction too low. Check the date font too. It should match the rest of the dial's typography, not look like a generic office printer.
Case, lugs, and crown
Genuine case finishing has sharp transitions between brushed and polished surfaces. Run a fingernail along the lug edges and you should feel a defined line, not a soft roll. The crown engraving is deep and centered. Pushers screw down or press with firm, short travel, and there is no lateral wobble. I also weigh the watch in hand. A fake often feels light or hollow because the caseback and midcase are thinner than they should be.
Strap, buckle, and paperwork
- Buckle stamping should be crisp and evenly spaced.
- Strap stitching is tight and consistent, with no loose tails.
- Box, booklet, and warranty card should match the reference and production period.
- Serial and reference engraving between the lugs should be sharp, not lazily lasered.
The bottom line
A good fake IW371785 can fool a photo. It rarely fools handling. Movement finishing, pusher feel, and dial depth are the three checks I trust most. If any one of them feels off, price the watch as a fake and move on.