A fake IW3270 is any watch sold as an IWC Pilot's Watch Mark XVIII that did not come out of IWC Schaffhausen, and the fastest single tell is the caseback: the genuine Mark XVIII uses a solid steel back with deep, crisp engraving, while most counterfeits show a shallow laser etch, a mismatched reference number, or a display back IWC never fitted to this line. Everything below builds on three criteria: reference accuracy inside the IW3270 family, component consistency from crystal to crown to date disc, and provenance in the form of paperwork, service history and how the seller answers basic questions.

What the IW3270 reference actually is

The Mark XVIII is a 40 mm automatic pilot's watch introduced in 2016 to replace the Mark XVII. It runs on the calibre 35111, a Sellita-based automatic with hacking, a quickset date and roughly 42 hours of running time, and IWC rates the case to about 6 bar with a push-pull crown rather than a screw-down crown. The IW3270 prefix covers several dial and strap combinations, which is why so many listings blur together.

• IW327001: black dial on a leather strap, the version most often copied and most often resold.
• IW327002: the same black dial on a stainless steel bracelet.
• IW327004: the blue dial Le Petit Prince edition.
• Mark XX references (IW3282xx): a later, different watch with a longer power reserve, frequently mislabelled as an IW3270 by careless sellers.

If a seller cannot state the reference and show it matching the caseback, you are already looking at a problem.

Check 1: caseback and reference engraving

Because the Mark XVIII has a closed back, this is where most fakes fail first. Look for even depth in the lettering, sharp edges on the numerals, correct spacing between the reference number and the Swiss markings, and no polishing haze around the engraving.

• Pros of this check: needs no tools, works from a good photo, and catches the majority of inexpensive copies immediately.
• Cons: better replicas use laser engraving that photographs convincingly, so a caseback alone is never proof.

Check 2: movement and beat rate

The genuine watch should run at 28,800 vibrations per hour with a smooth sweep and a clean, quiet rotor. Many inexpensive replicas use slower-beating or unmarked movements, or an unbranded Asian automatic with rough rotor noise. A watchmaker with a timegrapher can confirm beat rate and regulation in a minute, and opening the case is the only way to see finishing, jewel count and engraving on the rotor.

• Pros: movement evidence is hard to fake and is the strongest single argument for authenticity.
• Cons: requires a watchmaker, and opening a case you do not yet own is rarely possible before purchase.

Check 3: dial printing, hands and date disc

On the genuine dial the printed text is thin, matte and perfectly level, the applied indices sit flat against the dial, and the date disc is the correct shade with correctly shaped numerals. Replicas typically show slightly fat or glossy printing, indices that sit proud or crooked, lume that is a different colour from the hands, and a date wheel with the wrong font or a bright white disc under a black dial.

• Pros: visible in ordinary daylight photos and quick to judge once you know the correct font.
• Cons: early Mark XVIII dials and later service dials differ slightly, so compare against the correct production run.

Check 4: case, crown, crystal and lume

Look at lug shape and finishing, crown size and knurling, and the sapphire crystal with its anti-reflective coating. The crystal should be slightly domed with a bluish or faint sheen at an angle, not a flat, heavily tinted aftermarket replacement. Lume should glow evenly and fade gradually, not flare hard then die within minutes.

• Pros: case and crystal flaws are the hardest things for budget counterfeiters to hide.
• Cons: photographed watches hide case scratches and re-polished edges, which is why an in-hand inspection matters.

Check 5: strap, buckle, box and papers

Strap stitching, buckle engraving, spring bar quality and the feel of the leather are all consistent on the genuine article. Boxes, manuals and warranty cards are widely counterfeited, so paperwork confirms a story but never proves a watch.

• Pros: original box and card help with resale value and point to an honest seller.
• Cons: a full set can be bought separately and paired with a fake watch.

What to do before you buy

1. Ask for the reference number, then check it against the caseback in a close-up photo.
2. Request a movement photo or a timegrapher reading if the caseback is open or can be opened.
3. Compare dial printing, date font and hands against a known genuine example of the same reference.
4. Buy from a seller who accepts a return window and a watchmaker's inspection.
5. Treat prices far below the market for a genuine Mark XVIII as the strongest signal of all.

Use-case recommendation: if you want the Mark XVIII look at a fraction of the cost and accept that it is a replica with no brand service, buy knowingly from a seller who describes the watch as a copy rather than as a genuine IW3270. If you want resale value, service support and the ability to insure the watch, save for a genuine example with paperwork. The worst outcome is paying genuine money for a copy, and every check above exists to prevent exactly that.