The short answer
A fake IW371759 is worth your money only when three things check out before you pay: the case measures close to the real 41 mm across and roughly 13 mm thick, the two subdials sit on a true vertical axis at 12 and 6, and the chronograph resets to zero in one clean action on video. A box, a card, and a "Swiss made" print are decoration that any seller can supply. Proportions in a side-on photo and a reset clip are much harder to fake. Ask for both, then decide.
Know the watch being copied
The IW371759 belongs to IWC's Portugieser Chronograph family, the ref. 3716 line that was refreshed with an in-house automatic chronograph. The family formula is consistent: a 41 mm steel case about 13 mm thick, a bicompax dial with small seconds at 6 and a 30-minute counter at 12, leaf hands, applied numerals, a printed railroad minute track, sapphire crystal with anti-reflective coating on both faces, a display caseback, and a 3 bar rating. The current movement is calibre 69355, an automatic with a 46-hour reserve running at 4 Hz. There is no date window anywhere in this family, which becomes a useful filter later. Suffix codes in the line track dial color, case metal, and strap choice, and sellers use those codes loosely, so confirm the exact dial and furniture for 371759 against a factory photo before comparing anything else.
What to look for
Dial printing and subdial geometry
The railroad minute track should be crisp and evenly spaced all the way around, with no ink spread and no gap where the print meets the flange. The applied numerals should be faceted and sit flat to the dial. Study the gap between the 12 numeral and the top subdial ring: it should be tight and symmetric. Subdial rings should read as recessed, not stamped on. Small seconds and chrono hands should sit at the right height, clear of the dial and not skimming it.
Hands and applied markers
Leaf hands on the genuine watch are slim with a defined center ridge and even lume fill. Replicas often run thick, flat hands with sloppy paint edges. Check the seconds hand at 6 for a clean taper and a hub that matches the minute and hour hands.
Case profile and lugs
Ask for a caliper shot from the side. A slab-sided case that reads 14 mm or more usually hides a modified 7750 layout, and the lugs will look thick from above. Genuine lugs curve down at the tip and carry a polished bevel that meets the brushed flank in a straight line. Look for soft, rounded lug tips on cheaper builds.
Crystal and coating
Double-sided anti-reflective coating makes the dial look like it has no glass over it. Single-sided or uncoated crystals throw a blue or green sheen under shop lighting, which shows up in phone photos if you ask for an angled shot.
Chronograph behavior
Start, stop, and reset on camera. The minute counter at 12 should advance in steps, the reset should snap, and both hands should land exactly at zero. A seconds hand that settles a hair past 12, or a reset that feels mushy, is a reject regardless of how good the dial looks.
Caseback, movement, and rotor
The display back should show even bridges, clean screw heads, and a signed oscillating weight with decoration that does not look etched by hand. Reference and serial engraving should be cut into the metal, not printed on a sticker. Winding should feel smooth through the crown, and the rotor should turn without a metallic rattle when you tilt the watch near your ear.
Strap, bracelet, and clasp
On leather, check stitch density, edge paint, and whether the strap fits a 20 mm lug without squeezing. On steel, check end-link fit against the case, the signed clasp, and that the links articulate without slop.
Parameter bands that separate the tiers
- Case diameter: 41.0 mm, allow 40.7 to 41.3 mm on a caliper photo. Anything at 42 mm or above is a different case.
- Case height: 12.9 to 13.4 mm including the crystal. 14 mm or more points to a modified 7750 architecture.
- Lug width: 20 mm, so a spec strap fits without pinching.
- Movement spec: 28,800 vph, about 46 hours of reserve, running seconds at 6, 30-minute totalizer at 12. Running seconds at 9 or a 12-hour counter at 6 means the wrong base movement.
- Dial furniture: no date aperture, applied numerals, leaf hands, printed railroad track, signed crown.
- Water resistance: rated 3 bar on the original. Treat any replica as splash proof at best and keep it out of the pool.
Pitfalls to avoid
- Buying from a listing with front-on photos only. Without a side profile you cannot judge thickness, and thickness is the most common failure.
- Paying a "1:1" or "super clone" premium with no movement photos and no reset video.
- Accepting a date window. The ref. 3716 family does not have one, so a date aperture tells you the case or dial came from something else.
- Trusting dial text. "Swiss made" is printed, not earned.
- Expecting service support. IWC will not touch a replica, and independent watchmakers may decline or quote high because parts do not exist.
- Treating it as an asset. Resale on replicas is weak and the market is thin.
Questions to send the seller
- A caliper photo of diameter and height.
- A macro shot of the dial at an angle, to judge crystal coating and printing.
- A video of start, stop, and reset, with the minute counter visible.
- A photo of the caseback and rotor under good light.
- A photo of the crown and clasp signatures.
FAQ
How do I spot a cheap fake IW371759 from photos?
Look at the subdial positions first. On a correct build they sit on one vertical line with even spacing. On cheap builds the 12 counter drifts toward the center or the rings look flat. Then check thickness in a side shot and the clarity of the railroad print.
Does the movement really matter if the outside looks right?
Yes. The movement drives case thickness, subdial layout, and how the chrono feels in use. A watch built on a modified 7750 is usually thicker and has a different reset feel than the 69355 layout it copies.
Will anyone notice it is a replica?
Most people will not. Owners of the real watch will look at thickness, dial printing, and hand shape. Those are the same three things you should check before buying.
Can a watchmaker service a replica Portugieser chronograph?
Some will work on common base movements. Cloned in-house layouts are harder because parts are not catalogued, and many shops will refuse the job outright. Ask before you buy if servicing matters to you.
Is a replica safe to wear daily?
For desk wear, yes. Keep it away from water, avoid dropping it, and do not run the chronograph constantly. Treat the 3 bar rating as cosmetic.