Short answer
IW323720 is not a name IWC uses. The string joins the base reference IW3237 with a two digit variant code in one word. IWC prints the base reference and a case serial on the caseback. The variant code covers dial and strap choice. A listing that sells a watch under the words "fake IW323720" is a replica listing. The reference string is the first check, not the last.
IWC does not publish a full public archive of every reference. Confirm the model name, case size, and caliber for IW3237 with IWC or an authorized dealer before you compare a watch to a listing.
Checks on the watch
- Caseback stamp. The back should read IW3237 and a case serial, struck deep with sharp edges. Laser engraving on a replica sits shallow and gray.
- Serial match. The caseback serial and the number on the warranty card and booklet must be the same digits.
- Case size. Measure at the bezel with calipers. Replica cases run 0.5 mm to 1 mm off spec, and lug width is off too.
- Beat rate. A timegrapher reads 28,800 beats per hour on IWC's modern automatic calibers, eight ticks a second. Many fakes read 21,600, six ticks a second.
- Crystal. Sapphire with anti reflective coating shows one faint reflection from a lamp. An uncoated or poorly coated fake crystal shows two bright ones.
- Dial print. Under 10x magnification the logo strokes on a genuine dial have even weight. Replica print fills the serifs.
- Clasp code. Genuine IWC clasps carry a small code in addition to the logo. Replica clasps leave it out or change the font.
Where replicas fail
- Date wheel. Font, position in the window, and centering at 12 o'clock. Replicas sit the date high or left.
- Crown and pusher threads. Turn them. Gritty thread on a new watch points to a copy.
- Lume. Charge the dial under a lamp for 30 seconds. Genuine lume glows even. Replica lume patches out.
- Movement finish. Geneva stripes, perlage, and blued screws under a loupe. Fakes use plain plates and painted screws.
- Weight. A full bracelet on a steel IWC runs heavier than the copy. A scale settles this in seconds.
Price and paperwork
Compare sold prices, not asking prices. A watch with box and papers sells above the same watch without them, by 10 percent or more. When the price sits far below the band for that reference and condition, assume a replica or a watch with a bad title. Both cost the buyer money.
IWC sells new watches with a two year international warranty. IWC extends coverage to eight years when the owner registers the watch in the My IWC program. A seller who cannot show a registration, or who shows a card with a different serial, is a problem.
What settles it
Photos do not settle a fake IW3237. A watchmaker with the caseback off does. Budget $50 to $150 for an authentication and a written opinion. Ask for the movement photo before you send money, then have the watch checked on arrival. A seller who refuses an inspection is giving you the answer.