The best replica IW371736 builds share four traits: a case within a millimetre of the genuine Portugieser Chronograph, chronograph counters at 12 and 6, a Valjoux 7750-based automatic movement, and a sapphire crystal with anti-reflective coating on both sides. Those four checks decide whether a copy looks right on the wrist, and every section below works through them in order. Pull the official IWC specification for the reference before you compare listings, because sellers post dimensions that drift by a millimetre or two in either direction.

Case Size, Shape, and Finishing

This reference belongs to the Portugieser Chronograph line, which uses a wide dial opening, a thin bezel, and lugs that curve down toward the wrist. The genuine case measures just over 40 mm across and about 13 mm thick, so a copy that measures 44 mm or sits at 16 mm will look and feel wrong no matter how good the dial is. Ask for caliper photos of the case, the lug width, and the thickness from crown to caseback.

  • Pros: a correct case takes standard 20 mm straps; correct lugs keep the watch from overhanging a 6.5 inch wrist; brushing and polishing lines that follow the genuine pattern hide the copy at arm's length.
  • Cons: oversized cases are the most common flaw in cheap listings; sharp lug edges and cloudy polished flanks appear on low-tier builds; thick cases hide a cheap movement and add weight.

Best for: anyone with a wrist under 7 inches who wants a watch that sits flat under a shirt cuff.

Dial, Counters, and Printing

The Portugieser layout puts the chronograph minutes at 12 and running seconds at 6, with applied numerals and a rail-style minute track. Check the spacing between the two counters, the position of the date window if the reference has one, and the thickness of the printed text. A giveaway is a subdial hand that sits too short or a date window that cuts into a numeral.

  • Pros: applied numerals with proper polishing catch light the way the genuine ones do; a well-printed dial stays legible in daylight; correct counter spacing makes the whole face balance.
  • Cons: printed rather than applied markers look flat; over-glossy dials reflect studio lights but wash out outdoors; thin, pale printing fades at a glance.

Best for: buyers who care about reading the dial in normal light rather than in photos.

Movement and the Swiss Label

Most chronograph copies in this size run on the Valjoux 7750 architecture or a Chinese-made copy of it. A genuine Swiss 7750 runs at 28,800 vibrations per hour, hacks, and winds with a distinct rotor wobble; a quartz version ticks once per second on the running seconds hand and is the easiest thing to spot. Sellers use Swiss to mean a Swiss movement, Swiss parts, or nothing at all, so ask which movement is inside and whether the chronograph starts, stops, and resets at the pushers.

  • Pros: a 7750-based movement gives you a smooth sweeping seconds hand and a working chronograph; parts and service are available at most independent watchmakers; a display caseback shows a decorated rotor if the build is honest.
  • Cons: 7750-based copies add thickness; cheap clones lose time and reset poorly; quartz versions cannot fake the sweep and are obvious.

Best for: buyers who will use the chronograph and want a movement a local watchmaker can service.

Crystal, Caseback, and Water Resistance

A correct sapphire crystal with anti-reflective coating on both faces keeps the dial readable at an angle, which is where cheaper mineral glass fails. Look at the caseback engraving depth and the reference number, since shallow laser etching is a common shortcut. Treat any water resistance claim above 50 metres as unproven unless the seller pressure-tested the watch and shows the result.

  • Pros: double AR coating cuts glare; deep engraving looks correct under a loupe; a screw-down caseback with a proper gasket survives hand washing.
  • Cons: single-sided or missing AR coating produces a milky reflection; light engraving rubs away; unverified water resistance claims fail in a pool.

Best for: daily wear in an office or city setting, where splash resistance is enough and a pool is not.

Strap, Clasp, and Fit

The genuine line ships on alligator-pattern leather with a steel pin buckle or deployant clasp. Strap quality changes how the watch wears more than any other single part. Check that the strap tapers toward the buckle, that stitching matches the case metal, and that the clasp closes with a solid click.

  • Pros: a tapered leather strap holds the case in place; a steel deployant clasp reduces wear on the leather; quick-release spring bars make swaps easy.
  • Cons: thick, stiff straps make a thin case sit high; gold-tone buckles fade; glued straps split at the lug end.

Best for: buyers who plan to swap straps and want a case that takes standard fittings.

Practical and Legal Checks

Replica watches are counterfeit goods in most markets, including the United States, and customs can seize a shipment. Trademark holders enforce their marks, and no seller guarantee changes that. Beyond the legal side, ask about return terms, payment method, and whether the seller stocks spare parts before you commit.

  • Pros: a seller with a written return window limits your risk; spare parts availability extends the life of the watch; a seller who answers spec questions in writing is easier to hold to account.
  • Cons: no return policy leaves you with a bad copy; untraceable payment methods offer no recourse; seized shipments are rarely refunded.

Best for: buyers who accept the risk and want a seller who answers questions in writing.

Quick Verdict

Priority order: case size and thickness first, dial layout second, movement third, then crystal, caseback, and strap. If the case is wrong, nothing else matters. If the case and dial are right and the movement is a working 7750-based automatic, you have the version worth buying.