Short answer

A fake IW371447 fails at least one of four checks: movement, caseback engraving, dial printing, or serial number. The IW371447 is an IWC Portofino Chronograph. Its movement is caliber 79320, a Valjoux 7750 base that IWC modifies. Most replicas use a stock 7750 or a quartz module. Ask for a movement photo and a caseback photo before you pay.

What the reference is

IWC lists the Portofino Chronograph as a stainless steel chronograph with a 42 mm case, sapphire crystal, day and date at 3 o'clock, subdials at 12, 6, and 9, and an alligator leather strap. References in the 3714 family differ by dial color and strap. Dealer listings use the IW371447 number for more than one dial variant, so confirm the dial and strap against IWC's own catalog.

Movement check

Caliber 79320 runs at 28,800 vibrations per hour with about 44 hours of power reserve. The rotor carries IWC engraving. Bridges show Geneva stripes. Screws are blued. Fakes show a blank rotor, plain bridges, and no perlage. A quartz fake is the easiest to catch. Its small seconds hand at 9 o'clock jumps once per second. A mechanical 79320 beats 8 times per second.

Caseback, serial, and reference

Genuine casebacks carry laser engraving with crisp edges: the reference number, a serial number, water resistance in bar, and "Swiss Made." Fake engraving is shallow, rounded, or filled with paint. The serial and the reference must match IWC records for the production year. Replicas reuse one serial number across a batch. A serial that appears in three listings is a sign of a copy.

Dial, hands, and crystal

Genuine dials use applied indices with polished bevels and printed text with sharp edges. Fake indices sit flat and reflect light in patches. The date window sits centered with aligned numerals. Genuine crystals have an anti-reflective coating on both faces, so the dial loses reflection at an angle. Many replicas coat one face only. The crown logo must be crisp and centered.

Price

A genuine Portofino Chronograph on a steel case and leather strap sells in the low thousands of US dollars on the secondary market. Check recent sale records, not asking prices. Replicas sell from about $150 to $500. A seller who offers a steel Portofino chronograph for $400 is offering a copy, even if the movement ticks.

What photos cannot show

A photo cannot confirm the movement, the crystal coating, or water resistance. Ask for a video with the chronograph start, stop, and reset. Ask for the caseback and the movement. A seller who refuses any of the three removes the doubt.