The most reliable check on a claimed IWC IW371740 is a hands-on inspection by an IWC service center or an authorized dealer, because only they can open the case and match the movement, case number and engraving to factory records. Everything a seller presents, photos, box, papers, service receipts, counts as supporting evidence rather than proof. The criteria worth screening first are case geometry and finish, dial printing and subdial placement, movement behavior and pusher feel, and caseback markings checked against the paperwork.

Why this reference attracts copies

Any IWC chronograph with a clean, well-photographed dial becomes a copy target, because counterfeiters build from press images and dealer listings rather than from a genuine watch in hand. A dial that reads clearly in a catalog photo is also a dial that hides small errors at web resolution: compressed subdial rings, softer printing, or a date window sitting a fraction off center.

That gap between how a watch looks in a photo and how it looks under a loupe is where most bad purchases happen. Resolution hides the exact details that separate a genuine piece from a copy.

Criterion: case, crown and pushers

Case dimensions should match the published specification for the reference, measured at the widest point without the crown. Look at the transition between brushed and polished surfaces, which on a genuine case is crisp and consistent around the lugs.

• Check lug thickness and the inner curve where a strap meets the case.
• Look for a crown engraving that is deep, centered and evenly cut.
• Press the pushers: start, stop and reset should each give one distinct click.
• Check the crystal for a coating that turns slightly blue or purple at an angle.

Criterion: dial, subdials and date

Subdial positions are set by the movement underneath, not by the case designer. This is useful when you screen a watch, because a generic chronograph movement forces subdial and date positions into a layout that does not match the original. Compare subdial centers against clear reference photos, then check the date window for square edges and correct alignment with the surrounding printing.

• Printed text should stay sharp at the edges, with no bleeding or filler.
• Applied markers should sit level, with no glue visible at the base.
• Hand lengths should reach the correct track, not stop short of it.

Criterion: movement, winding and pusher feel

Wind the crown slowly and listen. A well-finished automatic chronograph movement feels smooth through the whole turn, with a rotor that moves quietly when the watch tilts. A low-grade substitute often feels gritty or loose, and the rotor can rattle when the watch is shaken gently near your ear. Ask the seller for a short video of the chronograph running: start, run for thirty seconds, stop, reset to zero. The reset should snap back to a clean twelve.

Criterion: caseback, case number and papers

Engraving quality decides many cases. On a genuine watch, the reference number, case number and metal markings are cut cleanly into the metal, with consistent depth. On a copy, they are frequently laser-etched shallow, uneven, or in a font that drifts from the brand's own. Match the case number on the back to the number on any warranty card, and match both to the seller's invoice.

Route 1: IWC service center or authorized dealer

This is the option that settles the question.

• Pros: trained staff, factory records, documented written opinion, and a service history that adds value if you later sell.
• Cons: an appointment or shipping step, a wait for the assessment, and possible fees.

Use this route when the amount at stake is significant, when the seller resists an inspection, or when the watch is described as unworn with full papers.

Route 2: Independent watchmaker or auction specialist

A watchmaker who services Swiss chronographs can read the movement quickly and tell you whether the finishing and component layout match what the brand uses.

• Pros: faster, often cheaper, and easier to arrange locally.
• Cons: no access to brand records, and opinions vary in depth.

Use this route for a first filter on a mid-range purchase, or when a brand inspection is impractical because of location.

Route 3: Seller screening before money moves

You can eliminate many bad listings without leaving your desk.

• Pros: free, immediate, and it works on remote sellers.
• Cons: photos can be staged, borrowed or retouched, so it never proves authenticity.

Use this route on every listing, then escalate to Route 1 or 2 before payment on anything expensive.

Legal and money reality

Counterfeit watches are trademark-infringing goods in most markets, and customs agencies seize them routinely, which means a cheap purchase can end with a lost parcel and no recourse. Resale of a counterfeit is restricted or illegal in many countries, so the money saved up front is often money you cannot recover later. If authenticity is the point, verify before you pay, and treat any seller who avoids that step as the answer to your question.