Short answer
A fake IW329100 almost always gives itself away in three places: the case finishing, the dial printing, and the movement's behavior over a few days. Not the logo. Fakes got good at logos years ago. What they still struggle with is the boring stuff, meaning the brushing direction on the lugs, the crispness of printed numerals at 6 o'clock, and whether the watch still runs after a weekend in a drawer.
If you only have photos to work with, here is the fast screen I run:
- Lugs should show a fine vertical brush with sharp, unrounded edges. Rep cases usually look polished or softly blurred where the brush meets the edge.
- Printed numerals should be flat, matte, and slightly raised. Fake dials tend to be glossy, thick, or slightly out of register.
- The date window should sit on the same plane as the dial, with a clean beveled cut. Replicas often have a stamped opening with a visible step.
- Hands should be flat, not domed, and the lume fill should stop short of the metal edge.
- Ask for a timed power reserve test, not a wrist shot.
What the reference number actually tells you
IW329100 is a full IWC reference, and the trailing digits matter. The base number identifies the model family, and the suffix identifies dial color, strap or bracelet, and market variant. Sellers who list a watch as "IW329100" without photos of the caseback are usually just copying a number from a listing. Ask for the full reference as engraved between the lugs and compare it to the papers. A mismatch there is not a small clerical error. It is the whole story.
This matters more with Pilot's Watch references than almost any other line, because the family shares so much DNA across sizes and variants. A replica built on a generic 40mm case can pass a squint test against several references at once. Only the engraving and the movement tie it to one.
Case and finishing
IWC finishing is restrained, not flashy. Look at the transition from the brushed case band to the polished bezel. On a genuine watch that line is crisp and even all the way around, and the polish is bright but not mirror-like. On most fakes the transition wanders, and one side of the bezel is visibly softer than the other.
Then check the crown. A screw-down crown should thread smoothly with no grit and seat flush. Replicas frequently have a crown that sits a hair proud or threads roughly after the first few turns. Water resistance claims on fakes are fiction, so never test one in water no matter what the listing says.
Dial, printing, and lume
Get a macro shot of the dial. The printed minute track is where replica dials fall apart. Genuine printing is dense and clean, with consistent stroke weight and no ink spread at the corners. Fakes show fuzzy edges, uneven spacing, and numerals that are slightly too bold.
Lume is the other tell. Charge it for thirty seconds and look in a dark room. Genuine Super-LumiNova glows evenly and fades gradually. Cheap lume glows hard for two minutes and dies. If the hands glow a different color or intensity than the markers, walk away.
Crystal and anti-reflective coating
The sapphire on these watches has coating on both faces, which produces a faint blue or purple sheen at an angle and near-total clarity straight on. Many fakes only coat the outside, so the dial looks slightly milky under angled light. A double-coated crystal will also look almost invisible against a dark dial, with reflections coming mostly from the dial itself rather than the glass.
Caseback, engravings, and the inner cage
Pilot's Watch cases use a soft-iron inner cage for magnetic protection. That cage adds weight and changes the sound when you tap the case. A fake will feel light and hollow. Genuine engraving on the back is laser-cut deep and sharp, with clean letterforms. Photo-etched replica engraving looks shallow and slightly grainy under a loupe.
Check the caseback tool marks too. A watch that has been opened by someone careless will show scrapes around the notches. That is not automatically a fake, but it is a reason to ask who serviced it.
Movement and power reserve
This is the test that ends most arguments. The current in-house automatic in this line is built for a long power reserve, measured in days rather than hours. Wind it fully, set it down, and check it after 72 hours. If it has stopped, the movement is not what the seller claimed. A replica with a generic Asian automatic will typically quit somewhere between 38 and 45 hours.
Listen as well. Put the watch to your ear and rotate your wrist slowly. A well-finished movement is quiet and smooth. A cheap one has a faint, uneven scrape from the rotor.
Strap, buckle, and small hardware
The tang or deployant should be machined, not cast. Look at the underside. Cast hardware has soft edges and a slightly porous surface. Genuine buckles are crisp and the spring bars are stout. Replicas ship with thin bars that bend when you change a strap.
Strap stitching is worth a glance too. Even spacing, tight thread, no fraying at the lug ends. It is a cheap thing to check and it correlates well with overall quality.
Box, papers, and price sanity
A complete set raises confidence but proves nothing on its own, since boxes and booklets are widely copied. Match the serial on the caseback to the warranty card and to the movement. Three matching numbers is a good sign. Two out of three is a problem.
Price is the blunt instrument. If a steel Pilot's Watch is offered at a third of the going used rate, it is either damaged, stolen, or fake. Nobody liquidates a genuine one at that discount for convenience.
A buying checklist I use
- Ask for the full reference between the lugs plus the serial, in one photo, in focus.
- Request a 72-hour power reserve result with a timestamped photo at start and end.
- Get macro shots of the dial print, the date window, and the caseback engraving.
- Ask whether the watch has been polished. An honest seller answers without hedging.
- Pay with a method that has recourse, and get the serial written on the receipt.
- Have a watchmaker open it within the return window. Budget for the fee and treat it as insurance.
One last thing. Replicas of this reference have gotten good enough that photos alone are not decisive anymore. Every tell above can be defeated by a careful seller with good lighting. The power reserve test and a look at the movement cannot.