The short answer
A fake IW371745 is worth buying only when the maker uses a proper 7750-based chronograph movement. The real reference runs IWC's calibre 79320, which is a modified Valjoux 7750, so a rep on an Asia 7750 keeps the subdial layout, the pusher feel and the case profile close to the original. Reps that swap in quartz or a thin automatic look fine in a listing photo and feel wrong the moment you set the time. That one detail is where most buyers get burned.
What the IW371745 actually is
It sits in the Portugieser Chronograph family: a steel case around 41 mm, a silvered or black dial, leaf hands, applied numerals, twin subdials and a date window. The appeal is proportion. The dial reads like something you would wear with a suit, but the movement underneath is a workhorse. A dress chrono with a tractor engine is a hard combination to fake badly, which is why this reference shows up so often in the rep market.
Why this reference copies well
The biggest tell on any chronograph replica is subdial spacing, and here the geometry comes free. Because IWC built the 79320 on a 7750 base, the copy movement drops into the same footprint. Subdials land where they should, the case stays within a millimetre of the original profile, and the pushers give you a real mechanical click instead of a soft push.
Second advantage: the dial. A flat silver surface with printed tracks and applied markers is far easier to reproduce than a sunburst blue or a deep guilloche. When a factory gets the printing crisp and the markers seated flat, nobody at the next table is going to call it out.
Movement options you will run into
- Plain Asia 7750. Cheapest working option, correct architecture, rough finishing.
- Asia 7750 with decorated and relabelled bridges. Same base, dressed to resemble a 79320. This is the sweet spot for most buyers.
- Swiss ETA 7750, often old stock or refurbished. Smoother winding and reset, and worth the premium if you plan to keep the watch for years.
- Quartz. Walk away from any listing that claims a mechanical chronograph at a quartz price.
What tends to get copied wrong
- Date font and window depth. The numeral should be thin and the aperture should sit close to the dial surface.
- Subdial rings. You want sharp concentric printing, not fuzzy dots.
- Crystal coating. Weak or patchy anti-reflective treatment makes the dial read grey instead of silver.
- Crown and pusher feel. Gritty threads, wobble, or a crown that will not seat properly.
- Strap and deployant. Thin leather, crooked stitching, a clasp that rattles when you move your wrist.
A checklist before you pay
- Ask for a macro photo of the date window and both subdials in daylight.
- Request a timegrapher reading plus a shot of the caseback off the watch.
- Get the movement type confirmed in writing, including Swiss or Asian origin.
- Ask for calipers on the watch itself, not the spec sheet.
- Confirm the chronograph resets to zero and stays there after several runs.
Price bands
Expect roughly $180 to $260 for an entry Asia 7750 build, $270 to $420 for a well-finished version with a decorated movement, and $500 and up once a Swiss 7750 or a hand-finished case is involved. Anything under $150 described as mechanical is a warning sign. Anything above $1,000 for this reference should come with a real reason, such as a Swiss calibre and documented service history.
Red flags while shopping
Photos that look like press images are often lifted from the genuine listing. If a seller will not send a fresh wrist shot with today's date on a handwritten note, assume the watch does not exist. Same for dealers who dodge movement questions, refuse a short video of the chronograph running, or claim a pressure test without showing the tester.
Bottom line
The fake IW371745 is a strong pick if you want the Portugieser look on a 7750 base, and a poor one if the seller hides what is inside. Buy the movement first, the dial second, and the story last.