Short answer
A fake IW371740 is a replica of the IWC Pilot's Watch Chronograph ref. 3717, a 42 mm steel chronograph built around the Valjoux 7750 architecture. Most replicas fail on four points: the movement, the dial printing, the day-date window, and the caseback engraving. If a seller will not show a clean movement photo and a serial number that matches factory records, treat the watch as fake.
What to have on hand
- A 10x loupe or a macro lens
- Bright, diffused light
- Digital calipers
- Reference photos of a verified example
- The seller's serial number and any service paperwork
Step-by-step authentication check
- Measure the case across the bezel. A genuine 3717 runs about 42 mm wide and roughly 14.5 mm thick. Replicas commonly arrive at 41 mm or 15 mm.
- Inspect the dial text under magnification. Genuine IWC and Schaffhausen printing sits sharp with clean edges. Replica printing looks flat, soft, or gray.
- Study the day-date window at 3 o'clock. The original aperture has square cut edges and discs that sit flush with the dial. Replicas show a beveled or oversized window and a wider date font.
- Check subdial placement. Running seconds sit at 9, chronograph minutes at 12, and the hour counter at 6. Replica dials crowd the counters together or shrink them.
- Look at the hands. Genuine hands are polished with flat tops and lume that stops at the frame. Replica hands show stamped edges and lume overflow.
- Press the pushers. A Valjoux 7750 based movement starts with a firm click, and the chronograph hand snaps back to zero on reset. Replicas feel mushy and the hand drifts off zero.
- Read the caseback engraving. Genuine lettering cuts deep and even. Replicas leave shallow letters with burrs or a gray lasered finish.
- Compare the serial and reference stamp. The reference should read IW3717 with the correct variant suffix, and the serial must be a discrete number rather than a shared or repeated one.
- Request movement photos with the caseback off. A genuine watch shows the calibre number on the bridge, correct jewel count, and a signed rotor.
- Wind and set the crown. Original winding feels smooth with steady resistance and clicks into each position. Replica crowns spin free or grind.
- Send the serial to an IWC service center or an authorized dealer before you pay.
Red flags that end the conversation
- A price far below the current market band for a steel 3717
- Stock photos instead of images of the actual watch
- No serial number, or a serial that changes when you ask twice
- A seller who refuses to open the caseback
- Papers printed on the wrong stock or with mismatched reference codes
Where fakes turn up
Replica 3717 chronographs move through classified ads, social media groups, and low-feedback auction accounts. The listing usually copies the wording of a genuine sale and swaps in a photo set from another seller. Ask for a dated image of the caseback with the serial visible, and compare that number against the paperwork. Any gap between the two confirms the watch is not what the seller claims. When in doubt, walk away and buy from a source that allows a return window long enough for an independent check.