A watch sold as IW371427 is a Portugieser Chronograph with an unverified reference number. The number does not match the reference lists published for that model. Confirm the reference, the caseback serial, and the papers with IWC before you pay.

The genuine watch behind the number

The IWC Portugieser Chronograph measures 40.9 mm across and 12.3 mm thick. Lug width is 20 mm. Water resistance is 30 m. Watches built from 2020 use the IWC caliber 69355, an automatic chronograph that runs at 4 Hz with a 46-hour power reserve. Older examples use caliber 79350, a Valjoux 7750 base at 4 Hz and 44 hours. US retail sits near $8,000. Steel examples on the used market trade between $5,000 and $7,000.

Case and dial checks

  • Case: 40.9 mm wide, 12.3 mm thick, polished bezel and case sides. A 43 mm case or a 14 mm thick case is not this watch.
  • Dial: applied numerals and an applied IWC logo on modern steel versions. Subdials sit at 12 and 6. Date sits at 3.
  • Hands: leaf shape, blued or rhodium plated. The small seconds at 6 moves in 8 steps per second.
  • Crystal: sapphire with an antireflective coating. Mineral glass on an IW371427 listing points to a copy.
  • Weight: a steel Portugieser Chronograph on a bracelet feels heavy in the hand. Plated brass does not.

Movement checks

A watchmaker can time the movement on a timing machine. A genuine 69355 or 79350 runs at 28,800 vibrations per hour, which is 8 beats per second. Copies use low-grade 7750 clones, simple chronograph modules, or quartz. Ask for an amplitude and beat error readout. A quartz second hand ticks once per second. A mechanical chronograph sweeps in small steps. Refuse the sale when the seller blocks an inspection.

Caseback, serial, and papers

Genuine IWC watches carry a caseback engraving with the maker name, the reference, and a serial number. The Portugieser Chronograph has a sapphire caseback, so the movement stays visible. The serial on the caseback should repeat on the warranty card and in IWC service records. IWC grants an 8-year international warranty when the owner registers the watch in My IWC. A seller who cannot show a card with a matching serial cannot prove the watch is real.

Price signals

A steel Portugieser Chronograph at $400 to $900 is not a used bargain. That price band belongs to counterfeit stock. Fake sellers also reuse one reference number across dial colors and case metals that IWC never paired. Ask for the reference on the caseback, then compare it with the dial color and the metal in the listing photos.

Verification steps

  1. Read the reference and the serial on the caseback.
  2. Compare the serial with the warranty card and the box label.
  3. Ask an IWC boutique or authorized dealer to check the serial in service records.
  4. Have a watchmaker open the case and time the movement at 8 beats per second.
  5. Measure the case with calipers: 40.9 mm wide, 12.3 mm thick, 20 mm lugs.
  6. Pay with a method that carries a dispute process.

Red flags

  • Price under $1,000 for a steel chronograph.
  • Printed dial markers or a glued, flat logo.
  • Quartz movement, or a caseback that cannot be opened.
  • Papers with a serial that does not match the case.
  • Seller refuses a timing test or a serial check.
  • Listing uses IW371427 for several dial colors and metals at once.

IWC reference data, case dimensions, and warranty terms change by production year. Verify the specific number on the IWC site or with a boutique. When a seller cannot supply that proof, walk away.