The quick answer
"Replica" and "fake" describe the same object here, and IW371631 belongs to IWC's Portugieser Chronograph family. If you are shopping a first copy of this reference, the deciding factors are three: case proportions, dial execution, and what actually ticks inside. Get those right and you have a watch that looks convincing on the wrist. Get them wrong and you have a thick, shiny thing that fools nobody who has handled the real one.
Why I Won't Write a Replica Buying Guide for the IWC IW371631
Everything below is what I check, in the order I check it.
What the genuine watch gives you
The Portugieser Chronograph is a 41mm steel case, roughly 12mm thick, with a sapphire crystal front and back and a 30m water resistance rating. The movement is IWC's in-house calibre 69355, an automatic column wheel chronograph with about 46 hours of power reserve. The dial layout is the signature bit: two subdials stacked at 12 and 6, a date window at 3, applied indices, and a thin feuille-style handset. Reference numbers inside this family differ mostly in dial colour, case metal, and strap, so a seller who cannot tell you which dial variant they are shipping is guessing.
Where copies get it right, and where they slip
Case and crystal
The Portugieser case is thin and flat on top, with a narrow bezel and long lugs that curve down. Cheap copies push the thickness past 14mm because they build around a bulky chronograph movement. You can spot that in a side profile photo before you ever see the dial. The crystal should sit almost flush, with a slight dome and a clear anti-reflective tint. A milky or heavily blue-coated crystal reads as budget from arm's length.
Dial and hands
Look at subdial spacing. On the real dial, the two counters sit close to the centre and leave generous open space at the outer edge. On many replicas they drift outward and the gap between them and the date window looks cramped. Printing is the other giveaway: the brand text and the numerals should be crisp and thin, not raised, not blotchy. The date font matters too. Genuine date discs use a plain, slightly narrow typeface, while copies often use a fat rounded font lifted from a generic movement.
Movement
This is where the tiers separate. Entry-level copies run quartz, and quartz chronographs give themselves away with a ticking seconds hand and a snap-back chrono reset. Mid-tier copies use an Asian 7750 derivative, which is a workhorse but adds thickness and has a different pusher feel. The best first copies use a column wheel clone and actually feel like the real thing when you press the pushers: light, precise, no mush. Ask the seller to name the movement. If they dodge the question, that is your answer.
The checks I run before paying
- Request a video, not stills. Ask for the chronograph started, run for a few seconds, then reset. Watch the sweep and the reset behaviour.
- Ask for a straight-on side shot so you can judge thickness against the lug profile.
- Ask for a shot of the caseback with the movement visible and the rotor in focus.
- Confirm the dial variant and the strap option in writing.
- Read the return policy. No returns means no deal for me.
Price bands, honestly
- Under $150: quartz, thick case, printed dial. Fine as a costume piece, not a convincing copy.
- $250 to $500: the sweet spot for most buyers. Automatic movement, good dial, minor tells on close inspection.
- $600 and up: top-tier builds with cloned movements, sapphire on both sides, and hand-finished cases. Diminishing returns start here.
For context, a genuine steel Portugieser Chronograph sits in the high four figures on the secondary market, which is why the copy market exists at all.
What nobody mentions
Resale on a replica is close to zero. Nobody buys one secondhand at anything like what you paid. Servicing is a problem too, since most local watchmakers will not touch a counterfeit, so you are relying on the seller or on a hobbyist. And in the US, importing a counterfeit watch is a customs violation, and selling one is trademark infringement. That is a real risk, not a footnote. Buy knowing that.
Bottom line
A replica IW371631 can look very close to the real thing if the case is thin, the dial is clean, and the movement is mechanical with a proper column wheel feel. Spend your attention on those three things and ignore the marketing language. Photos lie less than descriptions, and video lies less than photos.