The short answer
No single detail proves an IW328091 is fake. The reliable method is a stack of small checks that add up: case thickness, dial printing, date font, crown action, rotor noise, caseback engraving and the weight of the watch in your hand. A genuine IWC passes all of them. A replica usually fails two or three. Run the list in order and you will have an answer in five minutes.
Learn the reference before you judge the watch
Pull the official specs first. Case diameter, thickness, lug to lug, lug width, movement caliber, power reserve, water resistance. Write them down before you handle anything, because a seller who knows the watch will steer the conversation toward what looks right, and numbers do not care about that. Replica makers copy diameter well and thickness badly. Thickness is set by the movement inside, so a case that sits a millimeter and a half too deep with the correct dial size points to a substitute movement. Weight tells a similar story. Two steel watches of the same size should feel close in the hand. A watch that feels hollow, light or top heavy has a cheaper case and a cheaper engine under the dial.
Dial, hands and printing
Genuine dial printing sits flat and crisp under a loupe. Letter edges are clean, word spacing is even, and the brand text does not crowd the indices. Fakes tend to run thick, with heavy strokes, uneven gaps and markers that sit a hair off the minute track. Lume is another marker. On a real dial it is applied level with the marker edge, while fake lume is often domed, patchy, or a different shade under the same light. Hands get the same treatment. Genuine hands have polished bevels and a flat top surface, and the sweep is smooth rather than ticking in visible steps.
Date wheel
Check the date font against a reference photo, then check the position inside the window. A real date sits centered with even margins. Replicas often show an off center date, a bolder or narrower font, and a wheel that snaps late or drifts past midnight. If there is a magnifier, look at the edge. A genuine one is shaped and the magnification stays even across the whole window. A glued on lens with a wavy edge is a giveaway.
Movement: the hardest part to copy
Ask to see the watch running with the caseback off, or at least request a clear photo of the movement. Decoration is easy to fake and tolerances are not. Winding should feel smooth with a light, even resistance. A rotor that wobbles, rattles or whines is a cheap automatic, and those sounds do not improve with time. Check the beat rate if you can. A movement that sweeps in a slightly different rhythm than the reference is a different movement, no matter what is engraved on the rotor.
Case, crown and caseback
Look at the transition from the caseband to the lugs. Genuine cases are machined and then finished by hand, so the brushing stays in one direction and the polished bevels are sharp. Fakes show soft edges, swirl marks and polish that bleeds into the brushed surfaces. The crown should turn with clean clicks and no grinding. Caseback engraving is one of the easiest things to check. Real engraving is stamped or laser cut with crisp edges and even depth, while fakes look shallow and rounded. Reference numbers, case numbers and the brand mark should all match what the manufacturer published for that reference.
Bracelet, clasp and hardware
Run a fingernail along the edges of the links and the clasp. Real ones are deburred and finished on surfaces you cannot see. Fakes skip that step, so inner edges feel rough. Check the clasp engraving and the fit of the links. Genuine bracelets have almost no lateral play, while fakes develop a rattle within a week. Screws should sit flush and take a proper driver, not strip at the first turn.
In hand checklist, in order
- Measure thickness and compare it with the published spec.
- Weigh the watch and check the balance point on your palm.
- Read the dial with a loupe: letter edges, spacing, marker alignment.
- Flip the date forward through five days and watch the snap.
- Wind it, set it, and listen to the rotor.
- Inspect the case edges, crown action and caseback engraving.
- Flex the bracelet and feel the inner edges of the links.
- Compare the asking price with the current secondary market band.
If you are buying a replica on purpose
Plenty of buyers want the look without the price, and that is a personal call. What matters is honesty in the transaction. A replica should be sold as a replica, with the movement named, the case material named and the dimensions stated. When a seller lists a replica as genuine, or refuses to confirm what is inside, the watch is not the problem, the seller is. Price is the quickest filter. Anything far below the going rate for the reference on the secondary market is either a fake or a problem watch, and paperwork alone does not settle it.
Buy the seller first, ask for movement photos, and treat every detail on this list as a question rather than a verdict. One oddity can be a camera angle. Three oddities in the same watch is a pattern.