A replica IW371670 is a counterfeit copy of IWC's Portugieser Chronograph. The good ones get the 41mm case profile, the two-register dial with the 30-minute counter at 12 and running seconds at 6, and a movement that at least looks like IWC's in-house calibre 69355 through a display back. The bad ones get the subdial spacing, dial printing, and date window wrong, and those are the three things your eye catches before anything else.
The watch being copied
IW371670 belongs to the 3716 line, so the fundamentals carry over from the rest of the family. Steel or precious metal case, roughly 41mm across and 13mm thick, 20mm lugs, sapphire on both sides, applied Arabic numerals, leaf-shaped hands, a railroad minute track, and a date at 3. Water resistance on the original is only 3 bar, which matters because a lot of replicas claim more than the real thing and then leak.
Reference numbers inside the 3716 range differ mostly by dial color, case metal, and strap. That is useful when you are shopping a replica: pull up photos of the exact reference you want, not a generic Portugieser Chronograph, because dial color changes how obvious a bad print job looks.
Where replicas fall apart
Dial and printing
This is the tell. Genuine IWC printing is thin, evenly spaced, and sits flat against the dial. Cheap replicas print thick and slightly raised, and the numerals lose their sharp corners. Check the gap between the subdials and the center hands, and check that the date window is cut clean, not stamped with a visible edge.
Case and crystal
The Portugieser case is mostly polished with a soft curve into the lugs. Replicas often oversoften the lug tips or leave tool marks near the crown guards. On the crystal, look for anti-reflective coating on both faces and a slight blue or purple tint at an angle. No coating at all is a cheap build.
Subdials
Subdial diameter and position are the hardest thing to fake well. If the 12 o'clock counter sits too low or too close to the center, the whole dial reads wrong from arm's length.
Movement options you will see
- Quartz, usually sold as a budget model. Runs a sweep-less seconds and feels hollow when you tap the case.
- Decorated Valjoux 7750 or a Chinese clone of it. Reliable, thick, rotor wobble on the wrist.
- Clone of the 69355, with a column wheel and vertical clutch layout. Closest feel and closest look through the back, at the highest price.
QC checklist before you pay
- Ask for photos of the actual watch, not catalog shots.
- Check subdial spacing against the reference photo side by side.
- Look at the date font and window cutout under magnification.
- Confirm crystal coating at an angle.
- Listen to the rotor and check the pusher click feel.
- Verify caseback engraving depth and font.
- Confirm strap width at the lugs and buckle marking.
- Ask about the return window in writing.
Price tiers and what they buy
Budget tier gets you a correct silhouette and a wrong dial. Mid tier buys a decent 7750-based build with better finishing. Top tier buys the clone movement, a properly printed dial, and sapphire with real coating. Past that point you are paying for scarcity, not quality.
Questions worth asking a seller
Which factory built it, which movement is inside, what is the measured case diameter with calipers, and can they send a short video of the chronograph running and resetting to zero. A seller who dodges any of those is not worth the wire transfer.
One last note: nothing here replaces handling the real thing if you ever get the chance. Ten minutes with a genuine Portugieser Chronograph will teach you more about proportions than a hundred forum threads.