Short answer
A fake IW371741 shows up first in the caseback engraving, the date wheel font, and the finish on the small hands. No single photo proves a watch is real. Three or four checks together do. Ask for a straight-on dial photo, a caseback photo, and a timed run of the chronograph.
What the IW371741 is
Public reference data lists IW371741 as a Portugieser Chronograph. IWC lists a 41 mm case, 3 bar water resistance, and caliber 79350. That movement runs at 28,800 vph with a power reserve near 44 hours. The dial carries two subdials: chronograph minutes at 12 and running seconds at 6. The date sits at 3. Winding is automatic.
Confirm the exact variant before you compare details. IWC built the 3717 family over several years. Dial text, hands and caseback style changed between batches.
Fake IW371741: What Makes the Best Replica
Checks that settle the question
Caseback engraving
Read the reference number, the serial, and the lettering depth. Genuine engraving is cut with sharp edges and even spacing. Copies often show shallow laser marking, uneven digits, or a font that is too wide. Some 3717 watches have a solid steel back. Check which back your variant uses before you compare.
Date window and font
The date aperture should sit square to the dial print and level with the 3 o'clock marker. Copy dials often cut the window a fraction low or wide. Date numerals on genuine watches are thin and tall. Replicas tend toward thicker, rounder digits.
Subdials and hands
Feuille hands taper to a point. The taper should be clean, with no flat tip and no burr. Look at the small hands in both subdials. They should match the finish of the main hands, not painted. Subdial spacing is fixed by the movement, so a copy built on a stock 7750 layout places the two subdials farther apart than the real dial allows.
Chronograph action
Start and stop the chronograph. The pushers should feel firm, with short travel and a clean click. Reset should snap the hands back to zero in one motion. A soft pusher, a creeping reset, or a minute counter that stops short of 12 points to a cheap module.
Case finish
IWC does not publish a weight for this reference. Use case thickness, lug shape and finish instead. Case edges on genuine watches are polished, and satin surfaces meet the polished flank in a crisp line. Copy cases often round that line or polish across it.
What photos cannot show
Photos hide lume condition, crystal coating, crown thread feel and rotor noise. Ask for a short video with the chronograph running and the crown pulled to the time-setting position. A seller who refuses a video is a reason to stop. Replica quality also varies by factory and batch, so two copies of the same reference can differ in dial print and movement.
Price context
Used 3717 chronographs trade in the low to mid four figures. A price far below that range is the strongest single signal. Ask for service history, box and papers, then check the serial against IWC service records.