The top pick in the fake IW371445 market is the 40.9 mm steel build with a two-register dial and a modified Valjoux 7750 inside. That configuration is the only one that keeps the reference's proportions: a slim polished case, a wide silver dial, and a chronograph driven by a mechanical movement rather than a quartz module. Five criteria decide whether a given example earns that spot: case geometry, dial printing and register spacing, movement architecture, hands and crystal, then caseback engraving and strap hardware. Everything below is written for someone comparing listings, not for someone hoping a photo will settle it.
What reference IW371445 actually is
IW371445 belongs to the Portugieser Chronograph 3714 family. The case is stainless steel at 40.9 mm across, around 12.5 mm thick, with polished flanks, slim curved lugs and a push-pull crown. Inside sits calibre 79350, a Valjoux 7750 base that IWC reworked into a two-register layout: a 30-minute counter at 12 o'clock and running seconds at 6 o'clock. The 445 variant pairs a silver-plated dial with gold-plated leaf hands and applied numerals. Water resistance is rated at 3 bar, which tells you the back is sealed by a gasket ring rather than a screw-down system.
Those numbers are the yardstick. Any listing that cannot answer them with a caliper photo across the case at 3 and 9, plus a thickness reading with the back fitted, is asking you to guess.
Criterion 1: case geometry
The Portugieser case reads thin and wide on the wrist. A replica that adds half a millimetre of sidewall loses the whole character of the watch, and this is the most common failure.
Pros, what a good example gets right
- 40.9 mm measured across the case, not 42 mm with a note saying "close enough"
- Slim polished lugs that curve down toward the strap instead of sitting flat
- Crown sized and positioned so it does not crowd the caseband
- Caseback depth that keeps total thickness near 12.5 mm on a bench tool
Cons, where cheap builds fail
- Slab sides with a visible step between bezel and caseband
- Lug tips that sit proud of the wrist and leave a gap under the strap
- Oversized crown borrowed from a diver case
- Bezel too wide, which shrinks the dial opening and throws off the whole face
Criterion 2: dial and register spacing
On the genuine layout the two registers sit on the vertical axis, close to the centre, leaving wide open space on the silver dial. The spacing is dictated by the movement, so a mechanical replica using a 7750 base can reproduce it, while a quartz module often cannot.
Pros
- Applied numerals with faceted, polished surfaces that catch light at an angle
- Railway minute track printed thin and continuous, with no blur at the joins
- Silver-plated finish with a soft sheen rather than flat grey paint
- Leaf hands with a clean taper and a tip that reaches the track
Cons
- Printed numerals standing in for applied ones, visible as a flat edge in side photos
- Registers sitting too far apart or pushed toward the outer edge
- Heavy printing that fills the space between track and numerals
- Subdial hands that are too short or too thick versus the main hands
Criterion 3: movement
Three builds circulate. The 7750-based automatic is the only one worth comparing to the reference, the decorated automatic is a step down, and quartz is a different product wearing the same dial.
Pros
- 28,800 vph beat rate, so the sweep and the chronograph action feel mechanical
- Rotor and bridges that can plausibly carry engraving and Geneva stripes
- Reset snaps back cleanly from the pusher instead of clicking through a module
Cons
- Running seconds at 6 on a 7750 base runs through a transfer gear, and that gear is the first part to fail
- Quartz versions show a once-per-second tick on the chronograph hand and often run a dummy subdial at 12
- Decorated automatics often show a rotor engraving that does not match calibre 79350 markings
Criterion 4: hands, crystal and finishing
Ask for a macro shot of the dial edge at an angle. Anti-reflective coating on both faces of a sapphire crystal gives a faint blue or purple cast; a crystal with no coating throws a hard white reflection across the dial in every photo.
- Check that hour and minute hands align at 12 when the time is set
- Check that the chronograph hand returns to zero without drifting left or right
- Check hand height: hands stacked too low can foul the applied numerals
Criterion 5: caseback, engraving and strap
Most 3714 variants use a glazed back, so you should see a decorated movement with a signed rotor. Reference and serial engraving between the lugs should be cut, not laser-etched shallow, and the font should be consistent across both numbers. On the strap, look for alligator-grained leather with even stitching and a signed pin buckle or deployant, and check the strap thickness at the lugs because thin straps make a good case look cheap.
Red flags to walk away from
- A 42 mm case described as the correct size
- Subdials placed by eye rather than by movement geometry
- Printed numerals on a dial advertised as applied
- A chronograph hand that ticks once per second
- A running seconds hand that stutters or stops when the watch is tilted
- Shallow engraving with uneven letter spacing between the lugs
- No movement photo on a listing that claims a 7750 base
- A price that implies a genuine calibre rather than a copy of one
Matching the build to your use case
For daily wear, take the 7750-based build and set aside money for a service, because the seconds transfer gear is a wear item rather than an if. For occasional wear and display, a quartz example with correct 40.9 mm geometry looks right on a shelf and lets you down the moment someone presses a pusher. For photography or a gift, buy the mid tier with applied numerals and a well-printed track, since those two details carry most of the visual weight in images. If the plan is to pass the watch off to a dealer or a reseller as genuine, stop there: selling a counterfeit as an original is fraud in most jurisdictions, and the reference number is the first thing a trained eye checks.