Identification bracelets were an accessory worn by certain Starfleet personnel in the 23rd century.
History and specifics[]
In the year 2266, Crewman Hunt of the Federation starship USS Enterprise wore an identification bracelet during the landing party mission to planet K-G, during which he was turned into a plant. The bracelet allowed his fellow crewmembers to identify him. (TOS comic: "The Planet of No Return")