Short answer
IWC reference numbers that begin with IW3717 sit in the Pilot's Watch Chronograph line. The Portugieser Chronograph uses IW3716xx for the version sold from 2020 and IW3714xx for the version sold before that. I could not verify IW371772 in IWC's published reference lists. Ask the seller for a caseback photo. The engraved number and the model line must agree.
What the number tells you
IWC builds a reference from a line number plus a two-digit variant code. The line number sets the case, the dial layout, and the movement family. The variant sets the metal, the dial color, and the strap. Two watches that share a line number can differ by 2 mm in diameter and by several bar of water resistance.
If a listing says IW371772, confirm three items in writing: the line, the case diameter, and the water resistance rating.
Specs to measure on arrival
- Case diameter: measure across the case at 9 and 3, not across the crown guards.
- Case thickness: measure from the center of the caseback to the top of the crystal.
- Weight: a 40 mm steel case on a leather strap runs about 70 g to 90 g. A light case points to a thin alloy.
- Water resistance: keep the watch dry, or pay for a pressure test. Replica gaskets fail at low pressure.
- Crystal: sapphire rings on a tap test. Mineral glass sounds dull.
Dial and movement checks
On the Portugieser Chronograph, the 30-minute counter sits at 12 and the small seconds sit at 6. A stock Valjoux 7750 runs its small seconds at 9. A replica that shows seconds at 9 has the wrong layout for that model.
Most 7750-based copies use a modified rotor and a decorated bridge. The IWC 79350 in the genuine watch is a modified 7750 as well, so a movement photo is not proof on its own.
Run the chronograph. Start it, let it run 10 minutes, then reset. The hands must snap to zero. A bouncing reset means the reset hammer is worn.
Prices and limits
Replica prices track the movement, not the reference number. A 7750 copy costs more than a quartz copy. No replica carries an IWC warranty. No watchmaker with an IWC parts account will service one. Buy on the understanding that official repair channels are closed to you.
Before you pay
- Ask for a caseback photo that shows the full reference number.
- Ask which movement is inside, with a photo of the rotor.
- Ask for a pressure test result.
- Confirm the return window in writing.