Quick answer
A fake IW371628 gives itself away at the caseback and the movement, not at arm's length. The real watch is an IWC Portugieser Chronograph from the ref. 3716 family: 41 mm steel case, in-house calibre 69355 with a column wheel chronograph, sapphire crystal, and a see-through sapphire back. Replicas copy the outline well and fail on engraving depth, subdial spacing, hand finish, and chronograph reset. Check the reference between the lugs, the running seconds at 6 o'clock, and the way the chronograph hands return to zero before you look at anything else.
Identify the generation first
Ref. 3716 has been built in two forms, and a fake often mixes details from both. Watches made before 2020 used a modified Valjoux 7750, IWC calibre 79350, a 40.9 mm case, and a solid steel caseback. The current version runs calibre 69355 and has a display back. Ask the seller which generation the watch is, then match the caseback to that answer. An older style dial behind a display back, or a glass back on a watch sold as pre-2020, points to a replica or a watch built from mixed parts.
Dial and printing
Genuine dials use applied numerals and indices with polished facets, and the printing sits flat with sharp edges. Under 10x magnification, "IWC SCHAFFHAUSEN" and "PORTUGIESER" hold a clean edge and an even stroke weight. Fakes show thicker strokes, fuzzy edges, or ink that sits on top of the lacquer. On a genuine 69355 watch the two subdials sit recessed with a crisp step; replicas press them in shallow or leave a soft shoulder where the dial meets the counter.
Hands and subdial layout
The leaf hands on a genuine watch are polished on the top faces with an even grind on the flanks. The small seconds sits at 6 o'clock and the 30 minute counter at 12 o'clock, and both sit centered in their subdials with an even gap to the track. Fakes set the hands off center or swap faceted hands for flat painted ones. Look at the tip of the chronograph seconds hand: genuine hands taper to a clean point, replicas blunt it.
Case, lugs, and finish
Genuine case flanks are brushed with a fine grain, and the lug tops are polished with a sharp break line between the two finishes. That break should be a straight line, not a soft blend. Run a fingernail along the lug edge: a genuine case feels crisp, a replica feels rounded. Caseback screws on a genuine watch sit flush and line up, and the caseback edge has a machined step, not a cast curve.
Caseback engraving and movement
On a display back, the engraving around the sapphire should be cut deep with sharp inner corners. Laser-etched fakes look shallow and gray. Through the glass, calibre 69355 shows Geneva stripes on the bridges, blued screws, and a signed rotor. A rotor with no marking, a plain undecorated movement, or a movement ring held by clips instead of screws are all fake signals.
Strap, buckle, and hardware
Genuine watches ship on Santoni alligator leather with even stitching and a signed pin buckle or folding clasp. Check the stitching pitch, the lining, and the stamp depth on the buckle. Fakes use embossed cowhide, loose stitching, and a laser-etched logo that rubs off. Spring bars should be solid with a firm shoulder, not thin wire.
Box, papers, and numbers
Match the reference and serial on the warranty card to the caseback and to the movement. Ask for a photo of the card next to the caseback in one frame. Printed paperwork is easy to copy; the numbers are not. A seller who will not photograph the card beside the watch is hiding a mismatch.
Price reality
Ref. 3716 holds value on the secondary market, so a price far under the going rate for the same dial and generation is the oldest fake signal there is. Compare three current listings for the exact reference before you commit. A discount of 40 percent or more against those listings needs a reason, and "I need a quick sale" is not one.
Inspection checklist
- Request a straight-on dial photo and a sharp caseback photo before you discuss price.
- Read the reference between the lower lugs and confirm it shows IW371628.
- Measure the case across the bezel; the current 3716 measures 41 mm and the pre-2020 version 40.9 mm.
- Magnify the dial printing and compare stroke weight and edge sharpness to a known genuine photo.
- Confirm the small seconds sits at 6 o'clock and the 30 minute counter at 12 o'clock, both centered.
- Start, stop, and reset the chronograph, then watch how both hands return to zero.
- Inspect the movement through the display back for Geneva stripes, blued screws, and a signed rotor.
- Compare strap stitching, lining, and buckle markings against genuine reference images.
- Match the serial and reference on the warranty card to the caseback.
- Price the watch against three current market listings for the same reference and dial.
Red flags that end the conversation
- A price far below every comparable listing for the same reference.
- A seller who refuses caseback or movement photos.
- Reference engraving in the wrong font or filled with paint.
- Chronograph hands that do not snap back to zero on reset.
- A solid caseback on a watch sold as the current generation.
- A movement with no IWC markings or decoration.
- Box and papers that look freshly printed.
One failed check is enough to walk away. Two failed checks means the watch is a replica, whatever the listing says.