A fake IW371633 is a counterfeit of the IWC Portugieser Chronograph, and it usually exposes itself in three places: the movement behind the sapphire caseback, the subdial layout at 12 and 6, and the case finishing around the lugs. A genuine watch shows a correctly finished in-house calibre with sharp engraving and a dial where every element sits on the right axis, while most fakes fall back on a stock chronograph movement or a decorated plate.
What the IW371633 should look like
The reference sits in the modern Portugieser Chronograph generation: a 41 mm steel case, a slim bezel, leaf-shaped hands, applied numerals, a 30-minute counter at 12 o'clock and small seconds at 6 o'clock. There is no date window. The reference group covers several dial colours, strap and bracelet options, so confirm the exact dial variant against IWC's own product listing before you judge a specific watch.
The movement is the deciding detail. This generation runs IWC calibre 69355, a column-wheel chronograph with a power reserve of roughly 46 hours, and it is visible through a sapphire display back. If a watch sold as an IW371633 has a plain steel back, stop there.
Five checks that fail on most fakes
- Caseback and movement. Through the sapphire you should see Geneva stripes on the bridges, blued screws, a column wheel and clear IWC engraving. Fakes typically show a printed or stamped plate, a rotor with soft lettering, or a movement that does not match the calibre number on the back.
- Subdial layout and function. The 30-minute counter belongs at 12 and the running seconds at 6. A stock Valjoux 7750 or Seagull base puts seconds at 9 o'clock, so a correct layout means the maker had to modify or swap the movement. Watch the small seconds at 6: it should sweep, never tick once per second.
- Dial printing and markers. Genuine printing is thin, dense and perfectly level. The applied numerals are faceted and catch light along their edges. On fakes the lettering looks heavier, spacing between lines drifts, and the numerals sit slightly off the dial surface.
- Case and bracelet finishing. The case flanks are brushed with polished bevels that run in a straight, even line. Lugs have crisp inner edges. A fake usually shows rounded bevels, uneven brushing that crosses the edge, and a crown that is not engraved cleanly with the IWC mark.
- Proportions. The genuine case is about 13 mm thick and the lugs curve down toward the wrist. Many fakes add a millimetre or more because of the movement inside, which makes the watch sit proud on a strap.
What "fake" means at different price points
Shoppers use one word for very different products, and it helps to know which one you are looking at.
IW371633 Replica Watch Guide: How to Pick a 1:1 Build
- Quartz copies. Cheap, thin and easy to spot. The chronograph hands often work as decoration, the seconds hand ticks, and the subdials may not function at all.
- Mid-tier mechanical copies. Usually built on an Asian 7750 or a similar base with a modified layout. The proportions are close, but the movement is obvious and the finishing is flat.
- High-end replica builds. These copy the case, dial and hand set closely and use a movement with the correct subdial positions. They remain replicas: the movement architecture, engraving and long-term parts support never match the original.
Red flags in listings and packaging
- Only factory stock photos, with no macro shots of the dial, caseback or movement.
- A price far below the normal secondary market for the reference, with pressure to buy fast.
- Reused serial numbers. Fakes often carry the same number on every unit, which is easy to compare across photos.
- Boxes and papers with the wrong font weight, misspelled model names, or a warranty card that does not match the case number.
- No movement photos at all, or photos that are blurred exactly where the balance wheel should be.
Photos to request before you commit
Ask for a straight-on dial shot in daylight, a macro of the printing at 12 o'clock, a clear caseback image, a side profile, and a close-up of the clasp or buckle. Ask the seller to place a handwritten date next to the watch. If the reply is a stock image or a video that never shows the caseback, treat the listing as unsafe.
Frequently asked questions
Is every IW371633 with a display back genuine?
No. Some fakes now include a glass back with a decorated movement inside. Look at the quality of the stripes, the shape of the column wheel and the crispness of the engraving, not just the presence of glass.
Can a jeweller confirm a fake IW371633?
A watchmaker can open the case and identify the movement in minutes, which settles the question. Timers and pressure testers add useful data but the movement identification is the decisive step.
Does a ticking seconds hand always mean fake?
On this reference, yes. The small seconds at 6 o'clock should sweep in fine increments. A hand that jumps once per second points to a quartz module.