I'm willing to bet that they are injection moulded. If you can see a seam or a gate-point anywhere on the band it's probably a good indication. The 'raw material' will be either single part siloxane masterbatch granules with additional fillers and pigmenst added which is melted in the process, pumped into the mould and set (described simply enough); or a two part liquid silicone rubber which is combined in the right proportions, mixed, pumped and cured at high temperature.
As for the embossing or engraving, it's cut into the moulding dies at manufacture, and as the injection process causes the melt to conform to the shape of the mould it will conform to the detailing too.