A fake IW371410 gives itself away in three places: the subdial layout, the case thickness, and whatever is sitting behind the display back. The genuine watch is a two-register chronograph with no date window, a 40.9mm steel case roughly 12.3mm thick, and an IWC cal. 79350 visible under sapphire. If the small seconds hand at 6 o'clock ticks once per second, or the case measures 13.5mm and up with calipers, you are holding a counterfeit. Everything else you check is confirmation, not discovery.
What the real IW371410 is
The reference belongs to the Portugieser Chronograph 3714 family: stainless steel, silver-plated dial, applied Arabic numerals, leaf-shaped hands, chronograph minutes at 12 and running seconds at 6. IWC powers it with the 79350, a reworked Valjoux 7750 beating at 28,800 vph. Water resistance is 3 bar, lug width is 20mm, and the caseback is sapphire. Memorize those numbers before you look at any watch, because fakes fail on measurements long before they fail on finish.
Dial and hands
Subdials
The printed rings inside both subdials should sit perfectly concentric with the hands, with no gap on one side and crowding on the other. Watch the chronograph minute counter at 12 for a full minute: it should jump in one clean step. The running seconds at 6 should sweep in eight faint steps per second. A single tick per second means quartz, and quartz means the watch is not even pretending to be a 79350.
Hands and numerals
Look at the tips of the feuille hands. Genuine ones taper to a fine point with an even mirror polish and a counterweight on the chrono seconds hand that mirrors the same leaf shape. Fakes blunt the tip and leave the polish cloudy, which you notice as soon as the watch catches window light. The applied numerals should sit flat on the dial with sharp edges and a clean polish; a fake often shows rounded, slightly domed numerals with visible glue or a halo of shadow under them.
Printing
Lettering stays thin, even and crisp under a loupe. Fakes use a heavier, rounder typeface, and the spacing between the name and the town name is usually wrong. This is the tell I check first because it costs nothing and takes five seconds.
Case, crystal and caseback
Measure the watch. 40.9mm across, about 12.3mm thick, with a slim polished bezel and lugs that curve down sharply with a crisp bevel along the top edge. Counterfeit cases run thick and heavy, with fat lugs and a soft bevel that disappears under a fingernail. The crystal is sapphire with anti-reflective coating on both faces, so reflections are faint and slightly warm. A strong blue or purple glare usually means coated mineral glass.
Then flip it. The display back should be sapphire, with the reference, case number, water resistance and maker's name engraved on the outer ring. Genuine engraving is shallow and laser-sharp, still readable under a loupe. Fakes cut deep with rounded edges, and the numbers are often stamped rather than engraved.
Movement and pushers
Through the back you want a 79350: Geneva stripes across the rotor, blued screws, an engraved logo on the oscillating weight, and a balance running at 28,800 vph. Cheap automatic chronographs show rough finishing, an unmarked rotor, or a plastic spacer ring because the movement is too small for the case. Press the pushers as well. Start, stop and reset should have short, firm travel and a crisp click, and reset should snap the chrono hand back to zero instantly rather than letting it drift there.
Strap, buckle and paperwork
Genuine straps are alligator with even stitching and edges that stay sealed, and the buckle carries the maker's name plus the Probus Scafusia motto, cut cleanly. The warranty card, booklet and box should carry the same reference and serial as the caseback. A seller who cannot show that the caseback number matches the paperwork is a seller to walk away from, regardless of how good the watch looks.
Price is the fastest filter
Steel 3714s trade in the mid four figures on the secondary market, roughly $4,500 to $7,500 depending on dial and condition. Nobody sells a working IW371410 for a few hundred dollars. If the asking price sits far under market, the watch is stolen, broken or fake, and the seller knows which one it is.
Quick checklist
- Two registers, no date window at 3 o'clock.
- Running seconds sweep, not tick.
- Case 40.9mm wide and about 12.3mm thick.
- Sapphire on both sides with faint AR reflections.
- Rotor striped, engraved and correctly sized for the case.
- Pushers with firm, short travel and a snap on reset.
- Caseback serial matching the card and booklet.
- Price consistent with the open market, not with a bargain.