The best replica IW371601 on the market right now is the 41mm stainless steel version with a silver plated dial, applied numerals, and a working chronograph built on a modified 7750 base. That is the pick because the Portugieser Chronograph is an unusually unforgiving watch to copy: a thin polished bezel, a wide open dial, and two subdials placed on the vertical axis leave nowhere for sloppy work to hide. The criteria below are the ones that separate a wearable copy from one that looks wrong from arm's length: case diameter and thickness, dial printing and subdial placement, the movement architecture behind the exhibition back, crystal and finishing, strap quality, and the seller's quality control process.

Case Size and Profile

The genuine reference measures roughly 41mm across with a slim, stepped bezel and lugs that curve down toward the wrist. Copies that get the diameter right often miss the thickness, because the movement inside is deeper than the original calibre. A copy that sits two millimetres tall will wear like a different watch on a small wrist.

  • Pro: Most current 41mm copies match the genuine diameter closely and accept standard 20mm straps.
  • Pro: A correct thin bezel makes the dial look larger than it is, which is the whole point of the design.
  • Con: Many examples run thicker than the original, and the extra depth shows in profile photos.
  • Con: Caseback threading and gasket fit vary between batches, so water resistance claims deserve scepticism.

Use case: If you wear a 38mm to 40mm watch normally, ask the seller for a measured caliper photo of the case before you commit. If you wear 42mm and up, the thickness issue matters less.

Dial Printing and Subdial Layout

This is where the reference lives or dies. The chronograph counter sits at 12 and the running seconds at 6, both on the vertical centre line, with no date window anywhere on the dial. Leaf shaped hands, a fine minute track, and applied numerals finish the picture.

  • Pro: Good copies print the brand wordmark and the Schaffhausen line with crisp edges and no ink bleed.
  • Pro: Applied numerals that sit flat and catch light at the same angle as the hands read correctly on the wrist.
  • Con: Cheap batches place subdials slightly off centre, and the eye catches it immediately against the 12 and 6 markers.
  • Con: Some sellers ship versions with a date window at 3, which does not exist on this reference.

Use case: Buyers who care about macro accuracy should insist on straight-on dial photos plus a raking-light shot. Reflections reveal hand stack height and whether the subdial rings are printed or applied.

Movement and the Seconds-at-Six Problem

The genuine watch uses an in-house automatic chronograph calibre with a column wheel and a power reserve in the mid forty hour range. Copies almost always use a 7750 family base with a transfer gearset to move the running seconds from 9 to 6, because the original layout demands it.

  • Pro: The 7750 base is well understood, serviceable by most watchmakers, and parts are easy to source.
  • Pro: Chronograph start, stop and reset feel positive when the module is assembled with care.
  • Con: The extra transfer gears add drag, and a badly built example can stutter or stop at the six o'clock subdial.
  • Con: Through the sapphire back, decorated bridges will never match the geometry of the original calibre.

Use case: If you plan to use the chronograph daily, ask for a short video of the seconds hand running and the chrono resetting to zero. If you only want the look, this is the area where you can accept the most compromise.

Crystal, Caseback and Finishing

The original uses a domed sapphire crystal with an anti-reflective coating and a see-through back. Polished surfaces dominate: bezel, lugs, and case flanks are mirror finished, with brushing limited to small areas.

  • Pro: Sapphire on the front is standard at the better tiers and resists scratching in daily wear.
  • Pro: A properly polished case catches light in a way plated or roughly finished cases cannot.
  • Con: Some copies use mineral glass, which shows swirl marks within months.
  • Con: Engraving depth on the caseback is often shallow compared with the original.

Use case: Anyone wearing the watch with a suit should prioritise case polishing quality over caseback detail, since nobody sees the back.

Strap and Buckle

The reference is normally supplied on alligator grain leather with a pin buckle or a folding clasp. The strap is the cheapest part to upgrade and the fastest way to lift a mediocre copy.

  • Pro: Standard 20mm lugs mean aftermarket straps fit without modification.
  • Pro: A replacement strap in a better leather hides most finishing sins.
  • Con: Stock straps often feel stiff and the stitching is coarse under close inspection.
  • Con: Buckle engravings on lower tier copies are shallow or misaligned.

Use case: Budget for one good strap. It is the single highest return upgrade on this watch.

Seller and Quality Control

The seller matters more than the factory label on this reference, because variation happens between batches of the same nominal version.

  • Pro: Reputable sellers provide macro photos, a timegrapher reading, and a video of the chronograph working.
  • Pro: A seller who answers technical questions about the movement base is usually shipping a consistent product.
  • Con: Listings that promise Swiss made parts at impossibly low cost are a warning sign, not a bargain.
  • Con: Refunds and returns are difficult in this market, so pre shipment checks carry the weight.

Use case: First time buyers should ask for the same four checks every time: dial macro, caseback macro, timegrapher strip, and chronograph reset video.

Red Flags to Walk Away From

  1. No straight-on dial photograph. Lighting tricks hide misaligned subdials.
  2. A date window on a reference that never had one.
  3. Refusal to show the chronograph resetting to zero on video.
  4. Case thickness quoted vaguely or not at all.
  5. Claims of identical parts to the original calibre.

Which Version to Choose

For a first replica IW371601, take the 41mm steel case on the silver dial with blue hands, ask for the four QC checks, and plan to swap the strap. For a second watch or a gift, the same case with a decorated movement upgrade is worth the extra spend only if the seller can show the chronograph running cleanly. Skip anything with a date window, mineral glass, or a seller who will not send a timegrapher photo, because on a dial this open, every shortcut is visible.