The short answer: the fake IW371491 worth considering is the high grade automatic with a working 30 minute chronograph, twin registers at 12 and 6, and a case that lands within a fraction of a millimeter of the genuine watch. Four criteria decide that ranking. Case profile and thickness, dial printing and applied indices, movement architecture, and hand and case finishing. Everything below those four is a compromise you will notice within a week of wearing it.
What the IW371491 is before you compare fakes
The IW371491 belongs to the IWC Portugieser Chronograph family: a stainless steel chronograph with a twin register dial, the 30 minute counter at 12 o'clock and small running seconds at 6, leaf shaped hands, and applied indices on a clean, uncrowded face. Older production runs of this family used the 79350, a Valjoux 7750 base. Later runs moved to the in-house 69355. Dial colour variants within the family can share the same reference, so confirm the exact configuration against IWC's own reference records before you use any photograph as your comparison standard.
That twin register layout is the reason this reference is a popular target for replica makers, and also the reason most attempts fall short. Moving the running seconds to 6 o'clock while keeping a 30 minute counter at 12 requires either a movement built that way or a module stacked on top of one. Cheap builds fake it.
Tier 1: quartz and low grade automatic
These are the listings with the lowest numbers in the price column. The dial looks close in a phone screenshot and falls apart under a loupe.
- Pros: cheapest entry, light on the wrist, no service interval, fine as a costume piece.
- Cons: subdial spacing drifts toward the center, the chronograph seconds hand stutters or fails to reset to zero, cases run thick, indices are printed rather than applied, and the text on the dial is often too heavy.
Use case: a single event where the watch comes off before the night ends. Do not buy one expecting it to survive a summer.
Tier 2: mid grade automatic
This tier typically runs a 7750 derived chronograph, which is why it can offer a real 30 minute counter. It is the middle of the market and the most common answer to the question of what a fake IW371491 actually is.
- Pros: working chronograph with correct hand behaviour, sapphire crystal on most builds, dial layout that reads correctly at arm's length, serviceable by any competent watchmaker who knows a 7750.
- Cons: case thickness above specification, rotor noise, date aperture font and framing that do not match, pusher action that feels soft or gritty, strap hardware that betrays the build when handled.
Use case: daily wear by someone who wants the silhouette and accepts that a close inspection ends the conversation.
Tier 3: high grade automatic
The top of the replica market. These builds chase dimensions first and decoration second, which is the correct order.
- Pros: case diameter and thickness close to the genuine reference, applied indices with correct height, printed text with correct weight and spacing, anti reflective coating that reads neutral rather than blue, decorated movement with a rotor that carries the right engraving, crisp chronograph reset.
- Cons: highest price in the replica market, service can be awkward because parts are not standard, and the value still collapses the moment you try to sell it.
Use case: someone who wears the watch often, handles it daily, and understands the purchase is about appearance rather than ownership.
Dial and register tells
Put a loupe on the dial before anything else. Check the distance from the center of the dial to each subdial, since short spacing is the classic giveaway on a fake IW371491. Check whether the indices are applied metal with real edges or printed ink. Check the hand shape, because the leaf profile of this family has a specific curve that flat stamped hands miss. Check the date aperture for a frame and for correct font weight. Check the crystal coating, which should not flash purple.
Case, pushers and crown
Run a fingernail along the case flank. A correct case has a defined transition between brushed and polished surfaces, sharp lugs, and no softness at the tips. Press the pushers. A healthy chronograph start has a firm click and the stop and reset have distinct travel. Unscrew the crown and feel the thread, which should engage without wobble. Look at the caseback engraving under angled light, since shallow laser etching is a common shortcut.
Movement under the caseback
Ask for a movement photograph. Look for Geneva stripes or perlage that was cut rather than stamped, a rotor with legible engraving, and a balance running at 28,800 vibrations per hour. Ask what the power reserve actually is and how the chronograph is coupled, because a cam and lever system and a column wheel behave differently when you press the pusher. If the seller cannot answer, that is your answer.
Legality, service and resale
Counterfeit watches are illegal to traffic in the United States, and shipments are seized at the border. The Federation of the Swiss Watch Industry tracks counterfeiting as an industry wide problem, and customs authorities treat watch seizures as routine work rather than an exception. Practically, a fake IW371491 carries no manufacturer warranty, no service path through the brand, and no meaningful resale value. Buy it as a wearable object, not as an asset.
Quick recommendation by use case
- First replica, testing whether you like the look: tier 2, mid grade.
- Frequent daily wear, close up handling: tier 3, high grade.
- One event, low commitment: tier 1, and expect to replace it.
Whichever tier you choose, judge the watch on the four criteria from the top of this guide. Case, dial, movement, finishing. The tier names change between sellers. Those four checks do not.