The short answer
A fake IW371494 usually gives itself away in the first thirty seconds, and almost never at the spots people photograph for listings. Look at the gap between the two sub-dials, the edge of the printed text under 12, the way the chronograph seconds hand snaps back to zero, and the depth of the engraving on the caseback. Get those four right and you have filtered out most of what gets sold as a super clone Portugieser. Get them wrong and no box and papers will save it.
Below is the order I check things in, from the outside in.
First, confirm which reference you are looking at
The IW371494 belongs to the IW3714 family of Portugieser Chronographs, and the family shares a case and dial architecture across a lot of references. That matters for two reasons. Most authentication points carry across the whole family, so any clean IW3714 dial photo works as a comparison. And the small differences between references, dial colour, hands, strap, are exactly what sellers use to explain away mismatches. Pull the reference spec from IWC's own site before you argue with anyone about whether the hands should be gold or steel.
What you should expect from the family: a steel case around 40.9 mm across, roughly 12.3 mm thick, a domed sapphire crystal, a bicompax dial with running seconds at 6 and a 30 minute chronograph counter at 12, and IWC Caliber 79350 inside, which is a heavily reworked Valjoux 7750 running at 28,800 vph with about 44 hours of reserve.
The dial is where fakes get lazy
Sub-dial spacing
On a genuine 79350 based dial, the two sub-dials sit close to the centre and close to each other. The point of the layout is a compact, balanced face where the numerals have room to breathe. Cheap fakes push the sub-dials outward because the movement underneath has different geometry. Put a straight edge across the dial, or compare proportions against a known good photo shot at the same angle. If the sub-dials look like they are drifting toward the edge, walk.
Print and applied numerals
Genuine printing is thin, sharp and slightly raised. Fakes are either thicker and flat, or slightly fuzzy at the edges under a loupe. Check the I and W in the logo, the spacing of SCHAFFHAUSEN, and the small SWISS MADE at the bottom. On most replicas one of those three is off, usually the bottom text, which sits too low or reads too bold. Applied numerals should have crisp polished facets with no rounding at the tips.
Hands and the needle
Leaf shaped hands should have a distinct central ridge and a clean line where the polish meets the brushed flank. Fakes often use hands that are too thick, with a rounded ridge that turns into a soft blob under light. Length matters too: the minute hand should reach the minute track without touching it, and the chronograph seconds hand should stop dead at 12 on reset.
Case, lugs and caseback
Run a fingernail along the lug edges. Genuine finishing is a crisp transition between brushed top surfaces and polished flanks, with an edge you can feel. Fakes get over-polished here, so the transition is soft and the lug tips feel rounded.
The caseback is the other give-away. Look at engraving depth and the serial. Genuine engraving is cut, with clean walls and uniform depth, and the reference and serial are consistent with each other. Fake engraving is often laser-etched, shallow and slightly grey. The serial should match the paperwork, and the paperwork should match the era of the watch. A watch from one production run with a warranty card dated five years later is a question, not a bargain.
The chronograph is the hard part to fake well
Press the pushers. Genuine 79350 pushers have firm, short mechanical travel, and the start feels almost abrupt. Cheap fakes feel mushy, with a long spongy throw. Start the chronograph, let it run thirty seconds, then reset. The seconds hand should fly back and stop dead at 12, every time, with no overshoot and no second bounce. Then watch the minute counter at 12: it should advance cleanly rather than jump late.
Winding and setting matter too. The crown should click into each position with a positive detent, and hand-winding should feel smooth with a little resistance, not gritty. Screw the crown down and check the threads engage without wobble.
What good replicas do get right
Fairness matters here. The top tier of Portugieser replicas gets case proportions, crystal shape and general wrist presence close, and from two feet away most people will not know. What they still miss is dial printing at loupe distance, hand finishing, pusher feel, and the movement, which is either a decorated 7750 clone or a quartz conversion on cheaper examples. If a seller claims 1:1 and cannot show you a macro shot of the dial text plus a video of the chronograph reset, that is your answer.
A quick checklist
- Sub-dials close to centre and close to each other
- Thin, sharp print with correct spacing in the logo and SWISS MADE
- Leaf hands with a crisp central ridge
- Firm lug edges, no over-polishing
- Deep, cut caseback engraving with a serial that matches the papers
- Short, firm pusher travel and a dead stop reset at 12
- Price and paperwork that make sense for the reference and the year
If two or more of those fail, you are not looking at a watch with a story. You are looking at a fake.