The short answer: a replica IW371770 is a copy of an IWC Portugieser Chronograph, and the spread between the best and worst copies is huge. The good ones get the 41mm case silhouette, the twin-register dial and the pusher feel close enough that you need a loupe to argue. The cheap ones miss the subdial spacing by a millimeter and hide a rattly movement inside. Decide which one you are buying before money changes hands.
What the real IW371770 is
The reference sits in the Portugieser Chronograph family, the one with the round steel case, leaf hands, applied Arabic numerals and a printed railway minute track. Expect roughly 41mm across, around 13mm thick, a date at 3 o'clock and two subdials: chronograph minutes at 12 and running seconds at 6. Water resistance on the genuine watch is only 3 bar, so nobody is diving with it. The dimensions matter more than any other spec here, because case thickness is the hardest thing for a replica factory to fake in a photo.
The three tiers you will actually see
Budget builds use a quartz movement, a hollow case and printed subdials that do not function. Mid tier uses an Asian 7750 chronograph movement, which at least gives you working pushers. Top tier uses a decorated 7750 or a clone that mimics the layout of the in-house calibre 69355, with a column wheel look and better finishing on the bridges.
Genuine earlier Portugieser Chronographs ran calibre 79350, a heavily reworked Valjoux 7750. Current versions use the in-house 69355. That history is useful, because it means a 7750-based replica is not automatically wrong. It just has to be built well.
Details I check first
- Subdial spacing. The 12 and 6 registers should sit on the vertical center line and be equidistant from the center. If the top one crowds the date window, walk away.
- Date window. It should not cut into the outer minute track, and the font on the date wheel should be thin, not bold.
- Crystal. The genuine watch uses box-domed sapphire with inner anti-reflective coating. Flat sapphire or outer-only coating gives a blue cast in daylight.
- Pushers. No screw locks on this reference. They should travel short and firm, with a crisp reset that snaps the chrono hand back to zero.
- Caseback. Most versions are exhibition. Check the engraving depth, the font and the rotor decoration.
- Thickness. Ask for a caliper photo. A 7750 build that comes in at 15mm is not hiding anything.
What to ask the seller
- Factory and version number, plus the date that version was released.
- Which movement, exactly. Asian 7750, Swiss ETA 7750, or a decorated clone.
- Real photos of the actual unit, not catalog renders.
- Measured case diameter and thickness.
- Return policy and where it ships from.
Price and aftercare reality
Expect somewhere from about $80 for a quartz toy to $400 to $700 for a proper 7750 build with a decent dial. Anything above that is usually markup, and anything far below it is a quartz watch in a heavy case. Once it arrives, treat it as a mechanical watch that is not waterproof. Do not swim in it, do not shower in it, and if the chrono hand starts drifting on reset, that is your first sign the movement needs a service. A local watchmaker who works on 7750s can handle most of these for a reasonable fee, provided you tell them what it is.