If you have to pick one place to start with a fake IW371632, start with the movement and the caseback. On a replica of the IWC Portugieser Chronograph, those two areas fail before anything else does. The checks below are ranked by how much each one actually tells you: case geometry first, then dial furniture, then the calibre behind the display back, then engraving and reference formatting, and finally packaging and price sanity. Two failed checks is enough to walk away.

Check 1: Case Geometry, Crystal, and Pusher Feel

Treat the IWC reference page as the spec sheet for diameter, thickness, lug width and water resistance, then measure the watch instead of trusting the listing. A fake case is milled around a movement that is not the original one, so it commonly runs a fraction of a millimetre off in diameter or thickness, and the crown and pushers end up at the wrong height relative to the mid case.

Pros

  • Calipers catch most low tier and mid tier fakes in under a minute.
  • Nothing has to be opened or unscrewed.
  • Overall thickness is the hardest dimension for a replica case to hide.

Cons

  • A high end build can match published dimensions almost exactly.
  • Marketplace photos rarely include a measuring tool, so you often need the watch in hand.

Use this check first when a listing has no movement photos and the asking price is low enough to be tempting.

Check 2: Dial Furniture, Printing, and Subdial Spacing

The Portugieser Chronograph layout uses two registers, and the space between them is the giveaway. Look at the numerals: original watches use applied metal indices, while many fakes print them flat and thin. Check the printing weight of the brand name and the minute track under a loupe. Blurry edges, grey instead of crisp black, and a date window that sits off centre all point the same direction.

Pros

  • Dial details are visible in ordinary listing photos.
  • Applied versus printed numerals is easy to confirm with a raking light.

Cons

  • Good fakes get the dial right and fail elsewhere, so a clean dial proves little on its own.
  • Macro photos can hide printing flaws that show up under a loupe.

Use the dial check when you are comparing two candidates at the same price and need a tiebreaker.

Check 3: The Calibre Behind the Display Back

Ask for a photo of the movement through the caseback glass and compare it with the calibre listed for IW371632 on the manufacturer's own reference page. Two questions matter: is the movement mechanical at all, and does the register layout match the dial? Replicas built on a generic chronograph movement often keep an extra register at 9 o'clock or blank it with a plate, because the donor movement was designed for a three register layout and this reference uses two. A quartz fake has no rotor, no balance wheel and no winding feel.

Pros

  • Movement architecture is the hardest thing to copy at low cost.
  • Rotor engraving, jewel count and finishing are all verifiable against official specs.

Cons

  • Requires a clear, well lit photo that many sellers will not provide.
  • Decorated plates on high end fakes can mimic finishing convincingly in photos.

Use this check before any money changes hands when the seller claims the watch is fully original.

Check 4: Caseback Engraving and Reference Formatting

Engraving depth varies between laser and stamped work. Run a fingernail across the reference and serial numbers: crisp stamped characters have a defined edge, while shallow laser etching feels smooth. Compare the font, spacing and the position of the hallmarks with photos of confirmed examples. A caseback that disagrees with the dial variant is a hard stop.

Pros

  • No tools required.
  • Serial and reference formatting is a consistent, checkable pattern.

Cons

  • Casebacks can be swapped, so a correct back does not clear the watch.
  • Wear and polishing can soften genuine engraving and create false alarms.

Use this check on any watch sold as a full set, where the back is the first thing a buyer inspects.

Check 5: Packaging, Papers, and Price Sanity

Compare the asking price with current pre-owned listings for the same reference and dial. A steel chronograph offered far below the going rate is not a bargain, it is a signal. Boxes, booklets and cards are cheap to reproduce, so treat paperwork as supporting evidence rather than proof.

Pros

  • Price comparison takes minutes and needs no expertise.
  • Inconsistent serials between card, caseback and movement are easy to catch.

Cons

  • Genuine full sets are sometimes sold cheaply in estate sales.
  • Fake packaging has become good enough to fool a casual inspection.

Use this check as the final filter, after the four physical checks have already passed.

Which Route Fits Your Goal

If you want to avoid buying a fake, run checks one through five in order and stop at the second failure. If you already own the watch and want a verdict, take it to an authorized service centre or an independent watchmaker with a timing machine, since a rate and amplitude reading resolves most movement questions in minutes. If you are buying a replica knowingly, understand the legal position first: importing counterfeit trademarked goods is illegal in the United States and shipments are subject to seizure. Whichever route you take, the movement and the case dimensions remain the two checks that decide the outcome.