The short answer
If you found an IW371771 at a price that seems too low, it is almost certainly not a genuine IWC. If you are shopping replicas, the real question is not whether it is fake, since it is, but which tier of fake you are looking at. Five things settle that: the reference number on the caseback, the dial detail, the case and bracelet finishing, the movement behind the glass, and the price. Check them in that order and you will know within a few minutes.
First, confirm what IW371771 is supposed to be
IWC breaks its reference numbers into a family code plus digits that describe case material, dial, and strap. Two watches one digit apart can look identical in a photo and be entirely different references. That is why the first move is always the same: look the exact number up on IWC's own site or a dealer listing and write down the specs. Case diameter, lug width, crystal type, movement calibre, water resistance. Keep that list next to you for the rest of the checks.
If a seller cannot tell you the full reference and the calibre inside, stop there. Honest sellers answer that question in one line. The vague ones write "IWC automatic, mint condition" and hope you do not ask again.
The five checks that actually work
1. Caseback engraving
Genuine IWC engraving has consistent depth and a font that holds up under a loupe. The strokes are sharp, the spacing is even, and the reference and case numbers sit where they should. Cheap fakes use shallow, rounded lettering that looks like it was rubbed onto the metal. Watch for "Swiss Made" that drifts out of position, a serial number that appears on a dozen other listings, and a caseback that reads like a copy of a copy. Look at the weight of the letters, not just the words.
2. The movement
A display back is the single most useful thing you have. IWC chronographs in this family run on a heavily modified Valjoux 7750 base or an in-house calibre, finished with Geneva stripes, blued screws, and a signed rotor. Low-grade fakes show an undecorated movement, wrong text on the rotor, a plastic spacer ring, or a rotor that wobbles when you tilt the watch. If the watch is quartz, the running seconds hand ticks once per second instead of sweeping. That ends the conversation.
3. Dial and hands
Subdial spacing is the giveaway that photos usually hide. On a 7750-based chronograph the three counters sit in a fixed layout, and fakes built on a different base get it slightly wrong. Then look at the date wheel, because the font and the cut of the numbers are hard to copy. Applied markers should sit flat and flush. Printing should be thin and crisp. Fakes run thick and a little blurry, and the hands often have a rougher edge.
4. Crown, pushers, and how it winds
Screw the crown down and back out. The threads should engage smoothly, with no grinding and no wobble. Press the chronograph pushers. You want a short, firm throw, a crisp start and stop, and a reset that snaps back to zero with some authority. Mushy pushers and a crown that feels like it is chewing the threads are the cheapest tells on the whole watch, and they show up even in side-profile photos.
5. Strap, buckle, bracelet
Check the stitching, the buckle engraving, and how the end links meet the lugs. Genuine hardware has weight and a clean edge. Replica buckles are stamped thinner, the engraving is shallow, and the spring bars are soft. If you are buying on a bracelet, ask for a photo of the clasp closed and of the end link fit from underneath.
Why price is the loudest signal
Used IWC chronographs from this generation trade in the low to mid four figures depending on condition, box, and papers. Nobody sells a genuine one for a few hundred dollars, and no story about a divorce, a storage unit, or a friend who works at a dealer changes that. When the price sits in replica territory, ask the seller directly which tier it is and what movement is inside. A straight answer tells you more than any photo.
Where replicas still fall short
Even a top-tier first-copy watch is not a genuine IWC, and the gap shows in specific places: movement finishing, engraving depth, anti-reflective coating on the crystal, and the small mechanical flex of a real bracelet. If your goal is the look on the wrist plus the feel of a mechanical chronograph, that trade can make sense. If the plan is to pass it off as genuine to a buyer, expect the first jeweler who opens the caseback to end it.
What to ask before you pay
- The full reference number and the case number on the back.
- The movement calibre, and whether the rotor is signed.
- Close photos of the caseback, the crown side, the dial, and the movement.
- Whether the crown screws down properly and the pushers reset cleanly.
- Box, papers, and any service history.
- The return window, in writing.
Bottom line
The reference number, the movement, and the price tell you almost everything. Dial and caseback detail close the case. Spend ten minutes on those and a fake IW371771 stops being a mystery. It is just a watch that fails a check you already knew how to run.