Short answer

A watch sold as a replica is a replica. That covers every listing with "IW371415" in the title and a price under $3,000. The reference sits in the IWC Portugieser Chronograph family, and a genuine example trades in the four figures in US dollars on the secondary market. Box and papers push the number higher. No Portugieser Chronograph runs on a quartz movement, and none uses a mineral crystal.

What the reference number covers

IWC groups dial, case metal, and strap variants under the 3714 family of reference numbers. The last three digits track the variant. IWC's product page for your exact reference, plus the warranty card that ships with the watch, are the reliable sources for the spec. Photos on auction sites and forums get mixed up across references. Treat any spec sheet without a matching card as unconfirmed.

Case, crystal, and caseback

Portugieser Chronograph cases measure 40.9 mm across and about 12.3 mm thick. Lug width is 20 mm. Water resistance is 3 bar, printed on the caseback. The crystal is sapphire on the front. A plastic or mineral crystal picks up scratches after months of desk wear. Check the lug bevels under a lamp. Genuine cases keep a sharp line where the polished flank meets the brushed top. Fakes round that edge.

Movement checks

The 3714 chronograph uses the IWC calibre 79350, built on a Valjoux 7750 base. It beats at 28,800 vibrations per hour, or 4 Hz. Start the chronograph and watch the center seconds hand. A quartz fake ticks once per second. A mechanical movement steps 8 times per second and reads as a sweep. Reset the chronograph. On a 7750 base the hands snap back to zero with one firm push. Rotate the watch face down and back. The rotor on a 7750 base spins and the small seconds hand can twitch. A battery movement shows nothing.

Dial and hands

The subdial layout is the fastest dial check. One subdial counts chronograph minutes, the other runs the seconds. Fake dials print the IWC logo with fat strokes and uneven letter spacing. Look at the 12 marker and the subdial rings with a 10x loupe. Real print sits flat and sharp. Also confirm the date layout on IWC's page for your reference before you buy. Sellers mix references from the 3714 family, and a date aperture on a no-date reference is a mismatch.

Papers, serial numbers, and sellers

Genuine watches ship with a warranty card, a numbered caseback, and a serial that matches the card. Fake batches reuse the same serial across dozens of units. Ask for one photo that shows the caseback and the card together. Ask for a service receipt. A seller who will not open the caseback, or who will not send a movement photo, gives you a reason to walk away.

What photos cannot prove

A dial photo does not show the movement, the crown threads, or the case gasket. A watchmaker with a caseback tool and a timegrapher settles the question in 10 minutes. At full wind a Valjoux 7750 base reads 270 to 310 degrees of amplitude on a timegrapher, with beat error under 0.5 ms. A quartz fake shows no reading at all.