The fastest way to expose a fake IW371752 is to check the movement behind a display back, then match the case-back reference engraving to the serial. Those two details cost a replica maker the most to copy. The checks below follow that order of value: reference markings first, calibre architecture second, dial furniture third, external finishing fourth, and paperwork last. Any one check can be beaten. Two or three that agree give you a working conclusion.
1. Case Back Reference and Serial Markings
IWC cuts a reference number and a serial number into the case back of the Portugieser Chronograph. The characters have defined edges and consistent spacing. Replica cases often show laser-etched digits that sit flat, with wide gaps or a font that drifts between watches. A seller listing several IW371752 pieces with the same serial number is showing you a copied stamp.
- Strength: no tools needed, and it works from a listing photo.
- Limit: good replica cases now copy engraving closely, so this check alone proves little.
Use it when: you are screening an online listing and want a reason to walk away before you pay for travel or escrow.
2. Movement and Calibre Architecture
Portugieser Chronograph examples have used a chronograph calibre built on a 7750 base, and newer references use an IWC in-house chronograph movement. Confirm which calibre belongs to the reference you are looking at through IWC's published specification, then compare. Fakes lean on stock 7750 movements or Asian clones. Watch for a rotor with shallow engraving, bridges with a finish that looks painted, a jewel count that does not match, or a decorative plate hiding a movement whose subdial layout is wrong.
- Strength: the hardest element to fake at a low price point.
- Limit: you need a display back, a loupe, and some familiarity with chronograph movements.
Use it when: you can inspect the watch in person, or when the seller sends sharp macro photos of the movement and rotor.
3. Dial, Hands, and Crystal
The Portugieser Chronograph keeps a two-register layout with subdials at 12 and 6, applied numerals on most versions, and slim leaf-shaped hands. On an authentic dial the printing stays sharp under magnification, the applied markers sit level with the dial surface, and the hands carry polished sides with matte or brushed tops. Fakes show fuzzy printing, markers that sit proud or crooked, hand edges that look unfinished, and a crystal with weak anti-reflective coating.
- Strength: dial flaws show up in ordinary daylight photos.
- Limit: dials are the most copied part of the watch, and a high-tier replica can survive a photo review.
Use it when: the watch is in your hands and you want a fast pass before you move to the movement.
4. Crown, Pushers, and Case Finishing
Check the crown signature, the thread feel, and the pusher action. A genuine chronograph pusher has a defined start and a clean return with no side play. Replica crowns turn with grit, and replica pushers feel soft or stick. Look at the case flanks under direct light: brushed surfaces should run in one direction, and the line where a polished bezel meets a brushed flank should stay crisp rather than rounded.
- Strength: tactile checks are hard to fake and need no equipment.
- Limit: worn genuine watches can also have a gritty crown, so judge condition separately from authenticity.
Use it when: you meet a private seller and have two minutes with the watch on your wrist.
5. Box, Papers, and Service Records
Ask for the warranty card and the booklet, then compare the serial on the card with the serial on the case back. Replicas arrive as complete sets with printed cards, and the type on those cards does not match IWC print. A service invoice from an authorized repair center is harder to fake, and it tells you the watch has a documented history.
- Strength: mismatched paperwork is one of the clearest signals of a fake set.
- Limit: papers can be lost on a real watch, so absent paperwork is not proof of anything by itself.
Use it when: you are buying from a reseller who advertises a full set at a price that looks low.
6. The Legal Side in the United States
Counterfeit watches are not a gray-market shortcut. US Customs and Border Protection can seize shipments of counterfeit goods, and selling them exposes you to trademark liability. If you plan to resell, buy from a source that gives you a documented chain of ownership.
How to Use These Checks Together
- Screen listing photos against the reference and serial check.
- Request movement photos if the case back is a display type.
- Inspect the dial, hands, and crystal at magnification in person.
- Test the crown and pusher action.
- Match the paperwork to the case serial.
Two mismatches are enough to end the conversation. One mismatch on a watch with strong provenance is worth a second opinion from a watchmaker or an authorized service center before you decide.