Short answer

A fake IW371407 is a watch that carries the IWC reference number but does not use IWC parts, IWC assembly, or IWC finishing. The IW371407 belongs to the Portugieser Chronograph 3714 family: stainless steel case of about 40.9 mm, a two-register chronograph dial, and IWC calibre 79350, which derives from the Valjoux 7750. Confirm the exact dial and hand set for IW371407 against an IWC catalog or an authorized dealer, because the 3714 family covers many dial variants and the reference list is long.

Reference facts to check first

• Case: stainless steel, about 40.9 mm across, pushers at 2 and 4 o'clock, crown at 3.
• Dial: two subdials, one for chronograph minutes and one for small seconds, applied numerals or batons by variant, IWC logo below 12.
• Movement: calibre 79350, 28,800 vibrations per hour, about 44 hours of power reserve, automatic winding.
• Caseback: engraved reference number, serial number, and Swiss Made marking.

Movement checks

Genuine 3714 watches run IWC calibre 79350. That calibre comes from the Valjoux 7750 and runs at 28,800 vibrations per hour. Copies use an Asian 7750 clone, a Seagull ST19, or a quartz module. A quartz movement is the plainest tell: the small seconds hand jumps one step per second instead of sweeping. On automatic copies, the chronograph pushers feel soft and the reset action hesitates. Open a caseback only with a watchmaker. When the watch has a display back, the rotor engraving, perlage, and striping on a copy show rough edges or are missing.

Dial and case checks

Replica dials show thick paint on the numerals and the logo, uneven spacing between the IWC mark and the text below it, and subdial rings that sit off center. Check the date window: a printed date wheel with a mismatched font points to a copy. On the case, look at the lug edges, the polish on the bezel, and the crown threads. Genuine lugs have crisp bevels. Copies show rounded edges and gaps at the caseband. Weigh the watch. Copies with plated brass cases and base movements run lighter than a steel case with a 7750 inside.

Price and paperwork

Steel Portugieser Chronograph 3714 watches trade on the secondary market in the low thousands of US dollars. Value moves with dial variant, condition, service history, and box and papers. A listing far below market points to a copy. Ask for the reference number on the caseback, the serial number, and the warranty card. Compare both numbers with the paperwork. Serial numbers on copies repeat, so search the serial before you pay.

Legal note

Counterfeit watches are illegal to sell or import in the United States. US Customs and Border Protection can seize shipments, and trademark law lets IWC pursue sellers. The risk runs past the money spent on the watch.