Short answer

IWC lists reference numbers in the IW3716xx range for the Portugieser Chronograph. IW371650 does not appear in IWC's public product catalog as of this writing. A listing that calls a watch an IW371650 needs the reference confirmed against IWC records before anything else. If the number matches no production reference, the watch is a mismatched case back, a modified watch, or a fake.

How IWC reference numbers work

The format is IW plus six digits. The first four digits mark the family. IW3716 is the current Portugieser Chronograph, a 41 mm case in production since 2020. The last two digits mark dial, case metal and strap variant. IWC lists IW371605, IW371606, IW371609 and IW371617. A number outside that set is not proof of a fake on its own. Boutique editions and discontinued stock exist. It does mean you cannot confirm the watch from the number alone.

Checks that hold up

  • Movement: calibre 69355. Automatic, column wheel chronograph, 46 hours of power reserve, 28,800 A/h, small seconds at 6 o'clock, 30-minute counter at 12 o'clock, no date.
  • Pushers: chrono pushers at 2 and 4 o'clock engage with a short click and little travel.
  • Case back: reference and serial are engraved into metal, not printed on a sticker.
  • Size and weight: 41 mm across, about 13 mm thick in steel.
  • Dial: the printed minute track sits at the outer edge, and the two subdials align on the vertical axis.

What replicas miss

Copies of the Portugieser Chronograph run a Valjoux 7750 or a Chinese column wheel chronograph. Both differ from calibre 69355 in finish, in winding feel and in the lever shape under the balance. Print quality on the index and the Schaffhausen line is the common tell. Case back engraving is another: depth and edge sharpness on the real watch are higher than on a copy.

Price and paperwork

Steel IW3716 references sell new near $8,000 USD. Red gold versions run above $20,000. A seller asking $1,500 for an IW371650 is not offering a discount. Papers, a card with reference and serial, and a service record prove nothing by themselves. They can be printed.

Before you pay

Ask for a photo of the case back with the serial visible. Ask IWC or an authorized dealer to confirm that reference and serial pair. Have a watchmaker open the case back and read the calibre number on the movement bridge. If the seller refuses any of the three, walk away.