Short answer
IW371734 is an IWC reference number from the 3717 block. That block is the Pilot's Watch Chronograph Automatic. The case is steel and 42 mm across. The dial has two subdials: a 30-minute counter at 12 and running seconds at 6. A day-date window sits at 3. IWC used caliber 79320 inside, a modified Valjoux 7750 with 25 jewels, 28,800 vibrations per hour, and a power reserve of about 44 hours.
No photo proves authenticity on its own. The one test that settles it is the case number. Ask the seller for the reference and the case number, then confirm both with IWC or an authorized dealer. Genuine watches carry both engravings on the caseback, cut to the same depth and in the same font as the rest of that production run.
One caution. IW371734 shows up in listings with more than one dial color and strap combination. Verify the exact configuration against IWC records before you treat a difference as proof of a counterfeit.
Eight checks on a 3717
- Caseback engraving. Genuine: IWC, the reference, the case number, and SWISS MADE cut into the metal. Fakes: shallow laser etch or ink that sits on the surface.
- Case size. Measure with calipers. The 3717 case is 42 mm across. Copies often run 1 mm to 2 mm wide or thick.
- Subdial positions. Two subdials, at 12 and 6, with the day-date at 3. A copy built on a 7750 with a three-subdial layout is wrong at a glance.
- Day-date font and alignment. Genuine discs use IWC type in a centered window. Fakes show thick letters and discs that sit low in the frame.
- Dial print. IWC and SCHAFFHAUSEN are crisp, thin, and spaced apart. Copies show heavy print, broken serifs, and letters that drift toward the center.
- Soft-iron case. IWC Pilot's watches have an inner iron cage for magnetic protection. A watchmaker sees it with the caseback off. Most copies omit it.
- Movement. Caliber 79320, based on the Valjoux 7750, 25 jewels, 28,800 vph, engraved rotor. A correct beat rate proves nothing: copiers use ETA 7750s and Asian clones.
- Crystal and lume. Sapphire with an anti-reflective coating. Genuine crystals show a faint blue tint at an angle. Indexes and hands glow after a charge from a light.
Paperwork and price
Ask for the warranty card, the box, and service receipts. The case number on the card must match the case number on the caseback. The 3717 family ran from about 2006 to 2012, so cards dated outside that window are a flag.
Used 3717 chronographs sell for thousands of dollars. A listing at a few hundred dollars is not a genuine watch. High-end copies of this model also sell for several hundred dollars, so price alone does not separate a copy from a damaged or stolen original.
Before you pay
Request photos of the caseback, the crown, the clasp, and the movement. Ask for the case number in writing. Take the watch to an IWC dealer, a watchmaker, or a service center for a check. Pay with a method that lets you dispute the charge. If the seller refuses any of these steps, stop.
Limits: no public source lists every dial variant IWC built on reference IW371734. IWC's archive and a service center are the only places that can confirm a full configuration.