Answer first
A fake IW371613 is a copy of the IWC Portugieser Chronograph in its 41mm steel case, the ref. 3716 family with that specific dial and strap variant. Good replicas cost $350 to $600 and get the case shape, the vertical subdial stack and the domed crystal close enough that you need a loupe to catch them. They still fall short on the movement, the date font, the crown engraving and the pusher feel. Judge those four things and ignore the box, the papers and the seller's story.
What the real watch actually is
The genuine is a 41mm steel chronograph, about 12.3mm thick, with a silver or blue dial depending on the variant, applied Arabic numerals, leaf hands and two subdials stacked vertically: running seconds at 6, a 30 minute counter at 12, date at 3. Inside sits the calibre 69355, an in-house column wheel chrono with roughly 46 hours of reserve. Water resistance is 30m, which is modest and worth remembering, because plenty of listings quietly claim more. Retail sits in the high four figures, and the secondhand market holds value well. That gap is the whole reason the replica market exists.
Where replicas break down
Case thickness and profile
This is the fastest tell. Most replicas run 13.5mm to 14mm thick because the movement underneath is taller than the 69355. Put a caliper on it if you can. The lugs should curve down sharply toward the wrist, and the caseband should look thin in profile. A slab-sided case with flat lugs is a copy, no matter how good the dial is.
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Movement
Almost nothing in this price range carries a true clone of the 69355. What you get is a modified Asia 7750 with a decorated bridge, or a Chinese chrono module. Ask for a photo of the caseback off. A column wheel is a round, toothed part near the balance, and it should be visible. A bare cam and a lever is a 7750. Finishing on the bridges of a replica is applied by machine and looks uniform and shallow under a loupe, while the genuine has Geneva stripes with visible anglage on the edges.
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Dial printing and hands
The applied numerals should be thick and sit proud, with crisp edges and no rounding. Replica numerals often look slightly fat and sit a hair too low. The "IWC" logo above the date should be applied and sharp. Hands should be flat and polished with clean bevels. Look for dust under the crystal and for lume that spills past the frame.
Date wheel
Font weight is the giveaway. Genuine date numerals are thin, tall and evenly spaced. Replicas use a thicker font and sometimes sit the date slightly high in the window. Check the window edge too, since a sharp cut with a bevel is correct and a stamped square is not.
Crown and pushers
The crown should carry a deep, clean engraving of the logo, not a lasered smudge. Push the chrono pushers. Genuine ones start with a light, crisp click and return fast. A7750 pushers feel mushy and need a firmer push.
Price tiers, briefly
- Under $150: wrong case thickness, printed subdials, quartz or cheap auto. Skip.
- $250 to $350: decent dial, 7750 inside, thick case, weak date font.
- $400 to $600: best value. Correct thickness, sapphire, clean printing, decorated 7750.
- Over $700: you are paying for a name, not a better watch.
A checklist before you pay
- Get QC photos on a plain background, plus a close crop of the dial, the date window and the caseback.
- Ask for a timegrapher shot. Anything past plus or minus 15 seconds a day is a rough movement.
- Confirm thickness with a caliper photo.
- Confirm the strap material. Most replicas ship embossed calf, not alligator.
- Confirm a return window in writing. No window, no order.
- Pay by a method with recourse. Bank transfer to a stranger is a donation.
Bottom line
The best fake IW371613 is not the most expensive one, it is the one with an honest seller, correct case thickness and a movement you can see and hear. Spend your effort on photos and questions, not on the packaging. A replica is a replica. Buy it knowing that, and you will not be disappointed.