Short answer
A replica IW371631 is only worth the money if the seller shows you the actual watch: sharp dial photos, a chronograph that starts, stops and snaps back to zero, and the caseback engraving in focus. The IW371631 sits in the IWC Portugieser Chronograph 41 family, and that matters for anyone buying a copy. This dial is big, pale and mostly empty. There is nowhere for sloppy printing to hide. On cheap versions the tells are always the same: cramped or drifting subdials, soft edges on the applied numerals, and a chrono hand that lags when you reset it.
What the genuine watch is
The Portugieser Chronograph 41 runs a 41mm stainless steel case, roughly 13mm thick, with sapphire front and back and a display caseback. Inside is IWC's in-house calibre 69355, an automatic column-wheel chronograph with about 46 hours of reserve. The dial keeps the classic Portugieser arrangement: leaf hands, applied Arabic numerals, a fine rail track, and two counters, small seconds at 6 and chronograph minutes at 12.
Two things follow from that. First, the movement is not a generic 7750 with a module bolted on, so pusher feel and reset behavior are part of the watch's identity, not an afterthought. Second, the reference number matters. IW371631 is one dial and strap combination inside a line that covers several. If a seller uses stock photos of a different variant, that is your first warning.
Where replicas succeed and where they fall apart
Dial and printing
I look at the numerals first. On the original they are polished and applied, with crisp inner corners. Good replicas get close. Cheap ones look painted or slightly rounded, and the polish dies at the edges. Then the subdials. The distance from center to each counter has to match the original, and the rings should sit level with the dial rather than sunken under a thick layer of lacquer. Check the logo and the text under 12 for bleeding, uneven stroke weight, and lettering that is too heavy.
Case, crystal and finishing
The Portugieser case has broad flat surfaces and a narrow polished bevel. Replicas often over-polish, so the top of the lugs turns into a mirror and the whole watch reads fatter than it is. Ask for a side shot. The crystal should be nearly invisible at an angle, with a faint blue tint from the coating, not a milky haze. Lug width is 20mm on this line, so straps swap easily, which is a cheap way to lift a mid-tier copy.
Chronograph and movement
Most copies in this size use an Asian 7750 or a Seagull chronograph, sometimes a 7753 with the subdials rearranged to suit the layout. None of them are a 69355. That is fine if you accept it up front. Test the pushers: start, stop, reset several times. A column-wheel feel is light and precise, a cam system is heavier. The reset should snap to 12 every time. If the hand lands at 12:01, it will get worse, not better.
Caseback and markings
Engraving depth is a quick tell. Good cases carry crisp, readable text and a serial that is genuinely cut, not laser-etched pale gray. The rotor should spin freely and quietly. Movement decoration on a replica is often a printed plate over a stock movement, and there is nothing wrong with that as long as you were not told otherwise.
Price bands and what they buy
- Under $100: quartz or a rough automatic, poor dial print, plated case. Skip it.
- $150 to $300: decent automatic, correct dimensions, average finishing, loud rotor.
- $300 to $600: the sweet spot. Sharp dial, real sapphire, working chrono, decent leather or bracelet.
- Above $600: you are paying for small refinements. Worth it only if you know what you are looking at.
My checklist before paying
- Video of the chronograph running and resetting.
- Macro shot of the dial at 12, plus the subdial rings.
- Side profile for case thickness and lug shape.
- Caseback photo, in focus, with reference and serial visible.
- Timegrapher shot if one exists. Look for a rate inside plus or minus 15 seconds a day.
- Straight answers on water resistance. Most copies are splash resistant at best.
Living with it
Treat it as a mechanical watch, not a dive tool. Keep it away from showers and pools unless it has been pressure tested, and get it serviced when it starts losing time. The 7750 family is serviceable almost anywhere, which is one real advantage over the genuine article. On the wrist the 41mm case wears wide and flat, so a 7 inch wrist or larger carries it best.
Bottom line
The IW371631 is a hard reference to copy well because the dial leaves so much bare space. Buy from a seller who sends photos of the actual unit, pay in the middle of the price range, and check the chronograph before you accept delivery. Do those things and you get a handsome dress chronograph for a fraction of the real price. Skip them and you get a watch that looks fine in a listing and obvious in daylight.