What does “OEM” mean?

OEM stands for Original Equipment Manufacturer. In the watch trade it means a part made by the watch's own brand, as opposed to an aftermarket part made by someone else. Dealers use it for bracelets, clasps, straps, buckles, bezels, dials, crowns and boxes: “OEM strap” means the brand's own strap, not a copy or a third-party version.

OEM matters because genuine parts keep a watch closer to how it left the factory, which supports resale value and makes servicing simpler. When a part is sold separately, buyers check markings, reference numbers and finishing against known genuine examples, because aftermarket parts are sometimes described loosely. A genuine part can still be wrong for a particular watch, for example a bracelet from a different reference or a box from a different era, so OEM and correct are not the same thing.

An example post: “ISO: OEM Omega deployant clasp for leather strap, 20 mm, steel, for a Speedmaster.” A seller might reply: “OEM, genuine Omega, light marks, with code visible inside.”