Short answer
Check four things before you pay for a replica IW938450: the reference number itself, the movement inside, the case diameter, and the dial print. A seller who cannot show all four in photos is a seller to skip.
Start with the reference number
IWC builds reference codes as IW plus six digits. The first digits identify the watch family. IWC lists its current families and specs on its own site. Search there before you search a replica forum. If the number does not appear in IWC's catalog, the listing is using a label the brand does not publish. That does not prove the watch is fake. It does mean you cannot verify dimensions or materials against a factory page.
Movement
Replica IWC watches ship with one of three movement groups.
- Swiss ETA 2892-A2 or Sellita SW300-1. Automatic, 28,800 vibrations per hour, about 42 hours of reserve. Top tier.
- Japanese Miyota 9015. Automatic, 24 jewels, about 42 hours of reserve.
- Chinese clones such as the Seagull ST21 or Hangzhou 6300. Lowest tier, widest spread in daily rate.
Ask for the movement name in writing. Ask for a photo of the rotor and the balance wheel. Decoration plates hide a cheap base movement. A decorated plate is not a Swiss movement.
Case and crystal
Ask for the case diameter in millimeters and the lug width. Compare both numbers to the genuine reference. A gap of 0.5 mm is hard to see. A gap of 2 mm shows on the wrist. Check the crystal for anti-reflective coating on both faces. Single-side coating throws a blue or purple glare. Sapphire with double coating shows almost no glare.
Dial, hands, and date
Look at three areas in a close photo.
- Applied markers. They should sit level, with no glue squeeze-out at the edges.
- Hand length. Hour and minute hands should reach the chapter ring, not stop short.
- Date wheel font. Replicas often use a generic font that is wider than the original.
Price bands
Chinese-clone movements sit in the lowest band. Miyota sits in the middle. Swiss ETA or Sellita sits highest. A price far below the band for a claimed Swiss movement means the movement is not Swiss.
What you cannot confirm
Case alloy, water resistance, and lume compound are almost never documented for replica watches. Sellers claim 316L stainless steel and a 100 m rating. Neither claim is testable without a lab. Assume splash resistance only. Assume no factory warranty. Assume no parts supply for a repair five years out.