If you searched for a fake IW371651, you are in one of two places: trying to spot a counterfeit IWC Portugieser Chronograph before you hand over money, or shopping for a replica on purpose and wondering which build is worth owning. The top pick for the second group is the top tier build: a case near 41 mm, the correct vertical bi-compax dial, a working 30-minute counter, and an automatic chronograph movement that sits at the right thickness. Every option below is scored on four criteria: dial layout, case dimensions and finish, movement behavior, and caseback and strap detail.

What the IW371651 reference actually is

The IW371651 sits inside the IWC Portugieser Chronograph line, reference family 3716. The familiar spec is a steel case around 41 mm, two subdials placed at 12 and 6, a date window at 3, feuille hands, applied Arabic numerals, and an in-house automatic chronograph calibre in the 69355 family with a 30-minute counter and a sapphire caseback. The 3716 family spans several dial colors and case metals, so confirm the exact reference and its spec sheet on IWC's own listing before you compare anything. A seller who cannot name the reference they copied is already a red flag.

Tier 1: quartz and entry automatics

This is the bottom of the market and the easiest tier to identify. The case is often too thick, the dial printing is flat, and the subdials may be frozen decoration.

  • Pros: low outlay, light on the wrist, easy to replace if it dies.
  • Cons: a ticking seconds hand on a watch that should sweep, non-working subdials, printed numerals instead of applied metal, wrong date font, poor crown action.

Buy it if: you need a costume piece for photos or a party and will never let anyone hold it.

Tier 2: Valjoux 7750 based replicas

These use a real Swiss-derived automatic chronograph movement, which is why they feel convincing in the hand. The catch is layout. The 7750 architecture natively drives subdials at 6, 9 and 12, so makers either move the running seconds to 9, which is wrong for this reference, or bolt on a transfer module that adds height and noise.

  • Pros: genuine automatic winding, crisp pusher feel, sweeping subdial hands, repairable by a local watchmaker.
  • Cons: extra case thickness, rotor wobble, engraved rotor pretending to be IWC, date that flips at the wrong hour, wrong subdial positions on cheaper builds.

Buy it if: you want a mechanical chronograph you can actually use and you accept that a loupe will end the illusion.

Tier 3: clone movement builds

This is the tier that gets the dial layout right: chronograph minutes at 12, small seconds at 6, date at 3, and a case profile that measures close to the original.

  • Pros: correct subdial positions, believable thickness, better applied numerals and hand finishing, decorated movement with correct rotor text.
  • Cons: higher cost, patchy availability, service is difficult because parts are not standard, and no warranty worth the paper it is on.

Buy it if: the dial is what you care about and you plan to keep it long term.

The criteria, in order of importance

  1. Subdial positions and function. Seconds at 6, chronograph minutes at 12, both running. Anything at 9 fails.
  2. Case size and thickness. Ask for a caliper photo across the case and the caseback.
  3. Dial furniture. Applied numerals should cast a small shadow. Feuille hands should be polished on the bevel.
  4. Date window. Font, position, and a white disc that sits flush with the dial.
  5. Movement and caseback. A clear macro shot of the movement, not a stock render.
  6. Strap and clasp. Stitching density and buckle engraving are where budget builds fall apart.

Red flags in seller photos

  • Subdial hands that do not sit at zero after a chronograph reset.
  • No movement photo, or a photo lifted from another listing.
  • Claims of 1:1 quality with no measurement shots.
  • Factory renders instead of dated photos of the actual unit.
  • Pressure to pay outside any traceable method.

Verdict

For a fake IW371651 that holds up in normal conversation, buy in the clone movement tier and insist on a caliper photo and a movement macro before paying. If you want a working chronograph on a budget, the 7750 tier is the practical middle, provided you check which subdial carries the running seconds. Skip tier one unless the watch is purely decorative. If authentication matters at all, buy the real reference from an authorized dealer, because no replica passes a service-center inspection.