The string iw371640 does not match a current IWC catalogue entry as written, but it resolves to the IWC Portugieser Chronograph reference family IW3716, a 41 mm automatic chronograph sold in steel and gold across several dial and strap combinations. The top pick for any check on that string is not a listing photo, it is the genuine reference as IWC specifies it, because that is the only baseline a listing can be measured against. This guide works through six criteria in order: the reference number itself, case dimensions, case back markings, dial furniture, movement finishing, and price with paperwork.
What iw371640 likely points to
IWC references in this line begin with IW3716 and end with two digits that encode dial colour, case metal, and strap type. A trailing 40 reads like a truncated or mistyped sub-reference lifted from a marketplace title rather than a number IWC prints. On a genuine watch the full six digits appear together, stamped inside the case back and repeated on the warranty card, and all three sources agree with each other. A listing that shows one number in the title and a different number on the paper has a problem that photos cannot fix.
The specification baseline for an IW3716
IWC publishes the specification for each sub-reference on its own product pages. The family numbers to expect are these:
- Case: 41.0 mm diameter, about 13.1 mm thick, stainless steel or gold, polished bezel with brushed flanks on most versions.
- Crystal: sapphire, domed, with anti-reflective coating on both faces.
- Water resistance: 3 bar, which covers rain and hand washing and nothing more.
- Dial: two subdials, a 30-minute chronograph counter at 12 and running seconds at 6, no date window on the classic layout.
- Hands and markers: leaf-shaped hands, applied metal numerals, railway minute track around the perimeter.
- Movement: calibre 69355, automatic, column-wheel chronograph, roughly 46 hours of power reserve, 28,800 vibrations per hour.
Measure the case with calipers when you can. Copies tend to miss 41.0 mm and run thicker, because the movement inside is not a 69355.
Case back and reference markings
Factory laser engraving is crisp, shallow, and consistent in depth across the reference, serial, and metal stamps. Stamped or uneven marking is a common trait of copies. Both the reference and serial must be present, legible, and matched to the paperwork. Many IW3716 versions carry a sapphire display back, so ask the seller for photographs of the actual watch rather than catalogue renders. Run a finger around the seam: it should sit tight and even the whole way round.
Dial details that separate genuine from copy
- Applied numerals: real markers are separate metal pieces with polished facets that shift under light. Printed numerals sit flat and dull.
- Subdial rings: crisp concentric snailing with even spacing and no blur at the edges.
- Hands: leaf hands are polished and slightly domed, with clean edges at the tip and no burrs.
- Logo and text: correct letter spacing, sharp edges on the IWC letters, no ink bleeding into the dial.
- Chronograph action: the seconds hand returns to zero at once and lands dead on the marker when the pusher is pressed.
Movement and finishing
The 69355 is a column-wheel chronograph with a horizontal clutch, and its finish is part of the identification. Look for perlage on the plates, straight Geneva stripes on the bridges, polished screw heads, and an engraved rotor. If a listing shows a closed steel back and claims an IW3716, ask which sub-reference it is and confirm that number against IWC's own specification before anything else.
Three verification routes and their trade-offs
Authorized dealer or IWC boutique
- Pros: service records, factory parts, and a documented chain of ownership.
- Cons: highest price, waiting lists on popular dials, no flexibility on negotiation.
Best route when the watch is a keeper and resale value matters.
Established pre-owned dealer with papers
- Pros: lower price than retail, independent inspection usually available, return windows.
- Cons: condition varies, service history may be incomplete, you pay for the dealer's margin.
Best route for a first serious purchase where you want a return option.
Open marketplace listing
- Pros: widest selection, occasional bargains from private sellers.
- Cons: no inspection, no warranty, no recourse, and this is where reference strings like iw371640 tend to appear.
Use this route only after a watchmaker has opened the case, and only with payment methods that can be reversed.
Price and paperwork sanity check
Genuine IW3716 examples change hands at a wide range of prices depending on metal, condition, and whether box and papers are present. That spread is exactly why a price far below the rest of the market deserves scrutiny rather than excitement. Counterfeit watches cannot be serviced by IWC, cannot be authenticated by IWC, and are illegal to sell in the United States and the European Union. Customs authorities in both regions seize counterfeit shipments, and the buyer carries the loss.
Before you commit
- Get the full six-digit reference and serial in writing.
- Ask for caliper photos of the case and a photo of the case back from the actual watch.
- Confirm the sub-reference against IWC's published specification.
- Have a watchmaker inspect the movement and check that it is a 69355.
- Compare the asking price against completed sales for the same sub-reference, not asking prices.
- Pay only through a method with a reversal window.