Short answer
Four checks catch most fakes of the IWC Portugieser Chronograph ref IW371490: the movement under the display back, the case thickness, the dial printing, and the date window. A genuine 3714 has no date. Many replicas add one at 3 o'clock because the clone movement makes that step easy.
What the reference covers
IW371490 sits in the IWC 3714 block, the Portugieser Chronograph. IWC lists the steel case at about 40.9 mm across and about 12.3 mm thick. The dial carries applied Arabic numerals, leaf hands, a 30-minute counter at 12 o'clock, and running seconds at 6 o'clock. Water resistance is 3 bar.
Reference numbers inside the 3714 block split across dial colors, straps, and bracelets. Confirm the exact ref, dial, and finish on IWC's product page before you compare photos to a listing.
Movement
The 3714 uses IWC caliber 79350. That is a Valjoux 7750 base reworked by IWC: 28,800 vph, about 44 hours of power reserve, two registers, no date. Replicas use a Chinese 7750 clone. Look at the rotor engraving, the bridge finish, and the letter shapes in the text on the rotor. Clone rotors show shallow etching. Genuine plates carry Geneva stripes and polished screw heads.
Caseback and stamps
The 3714 has a sapphire display back. The rim carries International Watch Co. and Schaffhausen, plus the reference and case number. The serial number sits between the lugs. Fake engraving looks shallow and off center. Compare the caseback number to the number on the warranty card and to the movement.
Dial and hands
Genuine applied numerals have polished bevels and sharp edges. The dial text is thin, with uniform stroke width and clean spacing. Fakes show thick strokes, uneven spacing, and a soft edge under a loupe. Subdials on a real watch are recessed and snailed. Fakes print the rings flush with the dial. Genuine leaf hands have mirror-polished tops and crisp tips.
Case, crown, pushers
Check the crown for the IWC stamp and the fit against the case tube. Chronograph pushers should start, stop, and reset with a firm click and no side play. Brushed and polished case surfaces should meet on one clean line. Fakes show rounded lug edges and a thick case flank.
Price and paperwork
Used steel 3714 watches sell in the mid four figures in US dollars. A listing far under that range needs a movement check. A "super clone" at $500 to $1,500 is a replica. IWC does not sell through wholesale channels. No authorized dealer clears current stock at those prices.
Photos to request
- Caseback with the rotor and movement number in focus.
- Side profile at eye level, with calipers in frame.
- Macro of the dial at 12 and at 6.
- Serial number between the lower lugs.
- Warranty card and box in the same frame as the caseback.
What photos cannot prove
No photo set proves a watch. Numbers get re-engraved. Dials get swapped. A watchmaker with the case open is the single test that counts. If the seller blocks a bench check, walk away.