Short answer
A fake IW329156 fails four checks before anything else matters: the case-back engraving, the movement finish under a loupe, the bezel and crown action, and the dial print. Run those four first. If one of them is wrong, the watch is a replica or a counterfeit, and the rest of the inspection is wasted effort.
Most listings you will see are one of three things: a genuine Aquatimer Automatic 42, a high-grade replica sold as genuine, or a cheap counterfeit with a quartz movement. The gap between the second and third group is huge. The gap between the first and second is small enough that photos alone will not settle it.
The reference in one paragraph
IW329156 sits inside the IWC Aquatimer Automatic 42 family. That line uses a 42 mm steel case, a rotating outer ring that drives an inner dive scale, and IWC calibre 30120, a Sellita SW300-1 base that IWC modifies and regulates. A real one feels heavy for its size, has a signed screw-down crown, and carries both the case number and the reference on the case back.
Prerequisites
- A 10x jeweller's loupe.
- Digital calipers.
- A gram scale.
- Bright, raking light. A phone torch works.
- Factory photos of IW329156 plus owner photos from a watch forum.
- If the watch is not in your hand: a case-back macro, a crown-side profile, a rotor shot, and a straight-on dial shot from the seller.
Inspection steps
- Measure the case across the bezel and lug to lug with calipers, then weigh the head on the gram scale. Write the numbers down before you touch anything else.
- Compare those numbers with the published spec for the reference. More than about half a millimetre of drift in case size, or a few grams in weight, ends the inspection.
- Put the loupe on the case-back engraving. Genuine text is laser-etched with sharp, even edges and no burring. Replica engraving looks sandblasted, shallow, or has letter spacing that drifts.
- Read the case number and reference number and compare the font weight with the factory photo. Fakes often use a heavier, wider font.
- Turn the crown slowly to the first position and set the date. The click should be positive. A gritty or mushy crown points to a cheap movement or a worn clone.
- Turn the bezel ring. On a genuine Aquatimer the ring moves with firm, even detents and no lateral play, and the inner scale follows without lagging. A fake ring spins freely or jumps.
- Study the dial under the loupe. Applied indices should sit flush, be evenly polished, and show no glue at the edges. Date window edges should be cut square, not stamped.
- Compare the dial print with the factory photo. IWC uses consistent stroke weight and clean kerning. Fuzzy, thick, or uneven print is a fake.
- Check the hands. They should align to their markers at 12 and around the dial. Misaligned hands or a second hand sitting off centre are common on clones.
- Inspect the crystal at an angle. Genuine sapphire shows a faint blue-violet anti-reflective tint and almost no reflection head-on. Mineral glass on cheap fakes shows grey or green reflections.
- If the case back is open, loupe the rotor and bridges. Genuine finishing shows Geneva stripes with crisp edges, polished screws, and a signed rotor. Fakes show stamped stripes or an unsigned rotor.
- Ask for a timegrapher reading when you cannot open the watch. A genuine 30120 holds a tight rate band. A fake usually shows a large beat error or a rate spread wider than 15 seconds a day.
- Check the spring bars and strap or bracelet fit. Genuine IWC hardware seats firmly. Fake hardware rattles and leaves visible gaps at the lugs.
Red flags that decide it in seconds
- The reference on the case back does not match the dial and bezel configuration.
- The same case number appears on multiple listings. Clone makers reuse one number.
- The second hand ticks once per second.
- The seller refuses a case-back macro or a movement photo.
- The price sits far below market for a genuine example with box and papers.
- Dial or case-back fonts do not match the factory photo.
Replica, counterfeit, and "first copy"
Words matter when money changes hands. A replica is sold as a replica. A counterfeit is sold as genuine, often with forged papers and a fake box. "First copy" is a marketing term replica sellers use for their top grade, and nothing more. A first copy is still not a genuine watch, and no amount of polishing or service history changes that. If a seller uses first-copy language at a genuine price, you are looking at a counterfeit offer, not a replica sale.
If your IW329156 turns out to be a high-grade replica, that changes what you should pay and where you can get it serviced. Independent watchmakers will work on a Sellita-based clone. IWC will not touch it.
What to do with the result
If the four core checks pass and the numbers match spec, treat the watch as genuine until a watchmaker confirms it. If any check fails, walk away and keep the photos as a reference for the next listing. Save the case number you rejected. Reused numbers are the fastest way to spot the same fake twice.