The IW371704 is the stainless steel IWC Portugieser Chronograph with a silver plated dial, gold hands, gold applied markers, a 40.9 mm case, and the IWC calibre 79350. Counterfeits of this reference exist in large numbers, and most of them fail the same four checks: subdial layout, dial printing, caseback engraving, and movement finish behind the sapphire back.
Before You Start
- A 10x loupe or a phone macro lens
- Digital calipers, or a ruler accurate to 0.5 mm
- Bright, angled light
- Reference photos of an authentic IW371704 for side by side comparison
- The seller's box, papers, and service history, if any
How to Check an IW371704 Step by Step
- Confirm the two subdials sit on a vertical line at 12 and 6 o'clock. The IW371704 is a bicompax chronograph: 30 minute counter at 12, running seconds at 6. A third subdial, or a subdial pair at 9 and 3, means the watch is not this reference.
- Read the dial printing with a loupe. The IWC signature and the Schaffhausen text should be crisp, spaced even, and level with the dial surface. On fakes the letters run thick, thin, or uneven in height.
- Study the applied markers and the hands. Both are gold on this reference. The markers should sit flat against the dial with polished bevels that catch light along the full edge. Fakes use plated brass that looks dull or shows wear at the corners.
- Trace the minute track. The railway style track should be sharp, with every marker the same weight and the same gap from the chapter ring. Soft or broken printing is a common fake flaw.
- Measure the case with calipers. Expect about 40.9 mm across, about 12 mm thick, and 20 mm at the lug width. A case that measures 42 mm, or runs past 13 mm thick, is not an IW371704.
- Check the crown and the pushers. The crown should turn with light, even resistance. The pushers should travel a short distance, stop firm, and return with a snap. Gritty or mushy pushers point to a low grade movement.
- Check the crystal. The front sapphire is domed and, from straight on, shows almost no reflection. Fakes often use a flat or cloudy crystal with heavy glare.
- Reset the chronograph. Both hands should return to zero at the same instant, with no wobble and no drift. A slow or drifting reset is a fault that genuine examples rarely show.
- Turn the watch over and inspect the caseback engraving. The letters must be deep, sharp, and consistent. Reference and serial numbers on the IW371704 are engraved into the metal, never printed on a plate or a sticker.
- Look through the sapphire back at the movement. You should see a decorated movement with Geneva stripes and an engraved, signed rotor. A bare movement with a printed logo is a red flag.
- Examine the strap and the buckle. The reference ships on a black alligator strap with a steel pin buckle. Check the stitching, the lining, and the stamp inside the strap. Loose stitching and soft leather are typical of counterfeit sets.
- Trace the serial number. Ask the seller for the case number and the movement number, then compare both against any service paperwork. A serial that appears in more than one listing is a warning sign.
Red Flags That Show Up Again and Again
- A date window at 3 o'clock. The IW371704 has no date.
- Subdials at 9 and 3 instead of 12 and 6.
- Silver or rhodium hands and markers instead of gold.
- Dial text in a serif font or with uneven spacing.
- Caseback text that is shallow, filled, or misspelled.
- A rotor with a printed logo rather than an engraved one.
- A price far below the current market for a steel Portugieser Chronograph.
When to Walk Away
A watch that fails the subdial check or the case measurement is not worth a second look, no matter how good the price seems. If the seller refuses to open the caseback, hides the serial number, or declines to meet a watchmaker for inspection, treat the deal as dead. For a reference at this price level, a paid authentication from a brand authorized service center is the only check that settles the question.