Short answer
The IW371421 belongs to the Portugieser Chronograph 3714 family, and that makes the identification easier than you might expect. There is no exhibition back to inspect, so the tells live on the dial and in the case profile. Genuine specs: 40.9 mm across, roughly 12.3 mm thick, two counters with running seconds at 6 and a 30 minute totalizer at 12, leaf hands, applied numerals, no date window, solid steel caseback, 3 bar water resistance. Most fakes fail on thickness, subdial spacing, hand shape, printing, and price. If the watch in the photos is 14 mm thick, has a date at 3, or has subdials crowding the center, you already have your answer.
Five checks in under a minute
- Thickness. Ask for a caliper shot. Anything over 13 mm is wrong. The 7750 based replica movements are thick, and the case gets scaled up to hide them.
- Date window. The 3714 layout has none. A window at 3 settles the question.
- Subdial position. Counters at 12 and 6, spaced well apart, leaving a clean vertical channel through the middle of the dial.
- Hands. Leaf shaped, tapered to a point, with a subtle curve in the profile. Fakes use flat, blunt, or overly wide hands.
- Price. A running IW371421 in decent condition does not sell for four figures at the low end. If the number looks like a bargain, it is not one.
The dial is where most fakes fall apart
I look at the printing first. On a genuine dial the text is thin, black, and sits on top of the lacquer with hard edges. The word Schaffhausen under the logo is small enough that a bad copy smears it into a gray line. Look at the letterforms in IWC. The I should be a clean vertical bar, not a 1 with a flag, and the spacing between the three letters should be even. Some replicas get the logo close but lose the spacing, and that reads wrong from arm's length.
How to Spot a Fake IW371421 Watch
The subdials deserve a close look. Genuine counters are recessed with a fine snailed texture and a crisp stepped edge where the ring meets the dial. On fakes the recess is shallow, the texture looks stamped rather than cut, and the edge is soft. The small hands inside those counters should be the same leaf profile as the main hands. Copies often use plain batons or straight sticks there because they are cheaper to source.
Numerals are applied on the genuine, with polished edges that catch light at an angle. A printed numeral set is an instant fail. Check the printing of SWISS MADE at the bottom of the dial too. It sits low and close to the 6 counter, and replicas tend to float it higher or push it toward the crystal edge.
Case, lugs, and the shape you feel before you see
The Portugieser case is thin for a chronograph, and the bezel is narrow. That combination gives the dial a wide, open feel and makes the watch sit flat on the wrist. Fakes built around a standard 7750 with a chrono module end up taller, and the case sides look slabby. Ask for a side profile photo with the watch on a table. You want a gentle curve and a slim mid case. You do not want a brick.
Lugs are long, slim, and curve down. The lug tips on a fake are usually thicker and blunter, and the spring bar holes sit in the wrong place. The crown should be signed, and the two pushers should have short, firm travel. Mushy pushers with a long throw are a warning sign, though you can only test that in person.
Weight is a rough secondary clue. Steel has a density you feel immediately. Plated brass feels light and warms up fast in the hand.
The solid caseback and the movement you cannot see
Because the 371421 has a closed back, a faker can hide a cheap movement behind steel and nobody is the wiser from the outside. That is exactly why you judge the watch from the front and the profile. The inside of the caseback still matters if you can open it or get a photo. Look for deep, even engraving of the reference and serial, plus the IWC wordmark and Schaffhausen text. Laser etching that looks gray and shallow is typical of copies.
If you can handle the watch, run the chronograph. Start it, let it run a minute, then reset. Genuine caliber 79350 snaps both hands back to zero in one motion, and the minute counter advances with a crisp click. Fakes drag, overshoot, or fail to line up at zero. The sweep should be smooth at 28,800 vibrations per hour, not a one second tick. A ticking chrono hand means quartz, and quartz is not what this reference is.
Strap, buckle, and the small hardware
The original strap is alligator with fine, even stitching and a signed buckle. Replica straps are usually the weakest part of the package. Look for plastic edge paint, uneven stitch spacing, and a buckle with a soft logo stamp instead of a crisp engraving. The strap is easy to swap, so treat it as supporting evidence rather than proof.
What photos hide and what price tells you
Photos flatten thickness, hide hand profiles, and flatter bad printing. That is why I ask for a caliper measurement, a straight-on dial shot, and a profile shot before anything else. The price is the last filter. Used IW371421 examples trade in the mid to high four figures depending on condition and paperwork. A listing well below that range is not a lucky find. It is a different watch.
Bottom line
Judge the IW371421 on proportions and dial execution first. Get thickness, subdial layout, hand shape, printing, and the missing date right, and you will catch nearly every copy before you ever discuss the movement. The rest is confirmation.