During their trial on Kronos, the Klingon homeworld, Kirk and McCoy are furnished with hand-held translators to enable them to follow the proceedings which are done in the Klingon language. This piece has been screen-matched to specific use by Captain James Kirk himself, William Shatner. Features working lights.
During Kirk and McCoy's trial, we see dozens of Klingons in the huge, towering coutroom. To supply so many Klingons, highly-detailed latex masks were created that worked extremely well for background use. A few different head styles were created, then each was finished uniquely with painted details and wigs and facial hair.
In the pivotal trial scene, several Klingons can be seen in a "press box" at the edge of the courtroom, including one wearing this headset, presumeably listening to the translated testimony of Kirk and McCoy. The translator casing matches the Kirk version and is mounted to a headset. Features working lights.