Oyster Royal Chevron dial mid size ref. 6444Introducing the Rolex Oyster: the origin of the entire Rolex legacy. The first Rolex models, named Oysters, featured an innovative three part case design where all components screwed into each other. The fluted bezel, a signature element, was designed to screw down into the top of the case, securing the crystal with a gasketcomplemented by the grooves on the oyster case back. Now, it all makes sense, right? The Oyster became Rolexs introductory model