Short answer
IW371654 is an IWC reference number. The 3716 block belongs to the Portugieser Chronograph family. Replicas of these references exist. Most copies use a Chinese chronograph movement, a plated or lower-grade steel case, and mineral glass or single-sided coated sapphire. A genuine IWC Portugieser Chronograph uses a Swiss movement made or heavily modified by IWC, a sapphire display back, and case finishing that a replica factory does not match.
What the reference number tells you
IWC builds codes as IW plus six digits. The first four digits mark the model family. The last two mark case metal, dial color, and strap combination. IW371654 points to one specific Portugieser Chronograph variant. Confirm the exact case diameter, thickness, dial color, and strap with IWC or a reference database before you compare a watch against photos.
Where replicas give themselves away
Movement
Ask for a photo of the movement through the caseback. Recent Portugieser Chronograph references run an IWC 69000-family chronograph movement. Older ones used the 79350, a modified Valjoux 7750. Replicas usually carry a Seagull or Shanghai chronograph, a 7750 clone, or quartz. Look at the rotor engraving, the finish on the bridges, and the screw heads. Rough brushing and a printed rotor are common on copies.
Case and crystal
Measure the case with calipers. Published specs exist. A 0.5 mm difference is enough to reject the watch. Genuine IWC uses sapphire with anti-reflective coating on both faces. Under angled light the coating shows a faint blue or purple tint. Many replicas use coated mineral glass or sapphire coated on one side only.
Dial and hands
Check the printing of IWC and Schaffhausen, the applied numerals, and the gap between the two subdials. Replica dials often show thicker print, uneven lume, and a subdial hand that sits too high or too low. Portugieser feuille hands are thin and taper to a point. Copies are blunt and thicker at the tip.
Caseback and engraving
Genuine reference and serial numbers are engraved with a sharp edge. Under 10x magnification the lines are clean. Laser-printed numbers look soft and gray. The display back on a genuine watch shows Geneva stripes, blued screws, and perlage on the plates.
Weight and chronograph action
Weigh the watch head. Gold references weigh more than steel, and a steel copy can weigh 10 to 20 grams less than the real watch. Push the chronograph start and stop pushers. A cam or column-wheel chronograph has a light, defined click. Cheap 7750 clones feel stiff, and the reset can hesitate or snap back in two steps.
Prices
Steel Portugieser Chronograph references list near $8,000 to $9,000 USD at retail in recent years. Pre-owned examples trade near $5,000 to $7,500 depending on age, box, and papers. Replica sellers ask $200 to $1,000. A price far below the pre-owned range is the first sign of a copy.
Checks before you buy
- Get the reference and serial numbers. Confirm them with IWC or an authorized service center.
- Ask for a movement photo with the caseback open.
- Ask for caliper photos of the case diameter and thickness.
- Request the original box, papers, and service records.
- Pay for independent authentication before you send final payment.
What is not known
IWC does not publish production totals. No public list maps every IW371654 variant to a market or year. Treat claims about exact production numbers as unverified.