Short answer up front: there is no counterfeit IW329106 that survives a close inspection. IW329106 sits in IWC's Aquatimer Automatic 42 family, and the same four tells show up on every copy I have handled. The caseback engraving, the second crown that drives the inner dive scale, the movement behind the caseback, and the serial number are where replicas break down.
What the IW329106 actually is
The Aquatimer Automatic 42 is a steel dive watch with a roughly 42mm case, 300m of water resistance, a sapphire crystal, and a screw-down crown. What separates it from most dive watches is the internal rotating bezel. There is no click bezel around the crystal. Instead a second crown drives an inner dive scale, and IWC's SafeDive coupling is meant to keep that scale from drifting when you don't want it to move. The movement is an IWC caliber 30120, an automatic based on a Sellita SW300-1 platform, running at 4Hz with about 42 hours of reserve.
That combination is the problem for counterfeiters. An internal bezel with a linked second crown is expensive to reproduce. A decorated Swiss-base automatic is expensive to reproduce. Getting both right on the same watch, at scale, is close to impossible.
The checks I run first
- Caseback engraving. Genuine IWC engraving is crisp and shallow, with even letter spacing and a clean circular grained field. Copies show rounded edges, uneven depth, and lettering that fills in under a loupe.
- The second crown. On a real watch the inner scale moves in fine, defined steps and stops clean at both ends. On a copy it feels loose, overshoots, or spins past the stops.
- Crystal and dial. Genuine anti-reflective coating kills reflection from most angles. Fakes usually have a blue or purple cast and a dial print that looks slightly thick.
- Serial and reference pairing. The reference and serial on the caseback must match the paperwork and the movement. A mismatch is the single fastest disqualifier.
- Case finish. IWC brushes and polishes in separate planes with a sharp break between them. Fakes blur that line.
Movement side
Open the caseback and the story usually ends. The 30120 has a signed rotor, Geneva stripes, and blued screws. Counterfeit movements are often a low-grade automatic with a decorated rotor plate screwed over the top. Look at the balance wheel and the regulator; a plain, unmarked balance in a watch at this price is a red flag.
Where replicas land honestly
If you are knowingly shopping for a replica, be realistic. A good copy can look right across a table and get the case dimensions within a fraction of a millimeter. It will not hold water resistance to 300m, the movement will not run to Swiss chronometer tolerance, and service in ten years will be a problem. Nobody is going to authenticate it for you either. If you ever plan to resell, the math is bad.
Questions worth asking a seller
- Is the movement signed, and can you show the balance wheel?
- Does the inner bezel couple to the second crown and stop at both ends?
- Do the serial, reference, and any card or box agree?
- Has the watch been pressure tested, and by whom?
Get straight answers to those four and you will know more about the watch than most listings will ever tell you.