The short answer
A replica IW371745 is worth buying when the dial layout is right and the case sits close to the original 41 mm steel profile. Subdial placement at 12 and 6, a date at 3, and leaf hands are the parts you can verify in a photo. Thickness and movement finish come next. Price alone tells you almost nothing.
What the original IW371745 is
It is a Portugieser Chronograph 41 in stainless steel with a blue dial. The case measures 41 mm across. Inside is IWC's in-house calibre 69355, an automatic chronograph running at 4 Hz with a 46-hour power reserve, and the watch carries a date at 3 o'clock. The dial is a bicompax design: a 30-minute counter at 12 and running seconds at 6, with applied Arabic numerals and leaf-shaped hands. Water resistance is rated at 30 meters, which is the honest figure for a slim chronograph with a display back.
Hold those numbers in your head. Every replica claim gets measured against them.
The dial is where most replicas give themselves away
Subdial spacing
On the genuine watch the two counters sit close to the center, leaving generous open dial between them and the bezel edge. Replicas built on a stock 7750 with a transfer plate often push the counters wider apart or shrink them. That one proportion error is visible from arm's length, before you notice anything else.
Printing
Look for crisp, slightly raised printing on the minute track. The railroad track should be thin and even, with numerals and markers lining up cleanly. Soft or thick printing, or a track that fades toward the edge, points to a cheap pad print.
The date
The date window sits at 3. Replica date wheels often show the wrong font: too bold, too tall, or with the numeral sitting off center in the aperture. Ask for one photo with the date set to a single digit and one with a double digit. Both should look centered.
Case, thickness, and finish
The original is a slim watch for a chronograph, and reps based on a 7750 usually run thicker because the rotor and module stack need the room. I check thickness in real measurements, not in a listing. Brushing on the lugs should run one direction and stop at a defined edge. Polished bevels should be sharp, not rounded over. A case that looks soft at the lugs has been over-polished or was never finished well in the first place.
The movement question
Replicas of this reference come in three rough tiers.
- Entry: a basic 7750 with a spacer ring. Reliable enough, noisy rotor, wrong subdial geometry in some builds, and a case a couple of millimeters too thick.
- Mid: a modified 7750 or 7753 with a transfer plate to move the counters. Better layout, more parts that can fail, harder to service.
- Top: a decorated copy of the 69355 architecture. Closest visual match through the display back, smoother pusher feel, and a power reserve in the right neighborhood.
None of these is the real 69355. What matters is which one sits in the watch you are being shown, and whether the seller tells you straight.
Strap, buckle, and the small stuff
Alligator-pattern leather in a matching blue is the norm. Check the stitching, the taper, and whether the buckle tang has the right shape. Crooked stitching on a cheap strap is normal. Crooked stitching on a watch sold as top tier is not.
QC checks that catch problems early
- Dial photo straight on, no tilt, in natural light.
- Date set to 8 and to 22, to test font and centering.
- Case profile shot from the side with a ruler or calipers visible.
- Pusher test: start, stop, reset. The 30-minute hand must snap back to 12, not drift.
- Timegrapher reading if the seller has one. Rate and amplitude tell you more than any marketing copy.
- Lume shot in a dark room. Even glow, no bright spots.
Common mistakes buyers make
- Buying on the strength of a single hero photo.
- Ignoring subdial spacing because the dial color looks right.
- Assuming a decorated rotor means a better movement.
- Skipping the pusher test, then finding the reset hand parked at 3.
Bottom line
The replica IW371745 is one of the easier Portugieser references to fake well, because the dial is simple and the case is plain steel. That also makes the mistakes easy to spot once you know the three or four things to look at. Get the layout right, get the thickness close, and know which movement you are paying for. The rest is packaging.