Quick answer
A fake copy of the IW371649 is a third-party replica of the IWC Portugieser Chronograph: a 41 mm steel case, silver-plated dial, applied numerals, a railway-track minute track, two sub-dials at 12 and 6 o'clock, and a small date window at 3. Replica quality spans cheap quartz conversions to so-called 1:1 clones. The details that separate a passable copy from a bad one are dial printing sharpness, sub-dial spacing, the date aperture position, case thickness, and the finish on the movement and rotor.
Know the reference first
You cannot grade a copy without a baseline. The ref. 3716 family carries a 41 mm case and IWC's in-house 69355 chronograph calibre. Earlier Portugieser Chronograph generations (ref. 3714) ran the 79350, a modified Valjoux 7750. That matters because many replicas still clone the older 3714 layout and finish it as a 371649.
- Case: 41 mm steel, roughly 13 mm thick, brushed flanks with polished bevels
- Dial: silver-plated, applied numerals, leaf hands, recessed sub-dials
- Pushers: rectangular, stepped, firm without grit
- Crystal: box-domed sapphire with visible edge distortion at low angles
How to evaluate a replica IW371649
- Ask the seller for the case diameter and thickness in millimeters, in writing. Reject anything listed under 40 mm or over 14 mm thick.
- Request a straight-on macro photo of the dial. Check that the printing on the sub-dials is crisp under magnification and that no ink sits on top of the applied numerals.
- Measure the gap between the two sub-dials in the photo. On the genuine layout the spacing is tight and symmetrical; wide or uneven spacing points to a stock 7750 dial.
- Look at the date window. It should sit close to the 3 o'clock marker, beveled, with a white disc and black numerals aligned to the aperture.
- Ask for a side-profile photo. A slab-sided case with no bevel is the most common flaw on budget copies.
- Request a photo of the caseback and rotor engraving. Lettering should be laser-clean, uniform in depth, and correctly spaced.
- Ask which movement is inside and confirm the sub-dial function. Running seconds should sit at 6 and chronograph minutes at 12.
- Test the chronograph function on arrival: start, stop, reset. The reset should snap to zero without drift.
Common tells on weak copies
- Flat, printed sub-dial rings instead of properly recessed counters
- Hands that are too short or too wide at the tip
- Pushers that wobble or sit proud of the case band
- Rotor engraving that is shallow, filled, or misaligned
- Date numerals that sit off-center in the aperture
Set expectations before paying
Ask the seller for the return window and whether the watch ships with the movement named in the listing. Request photos of the actual unit, not catalog renders. Keep the transaction documented. A replica is sold as a replica; representing one as a genuine IWC is fraud, and no seller should suggest otherwise.