Beginning with Wrath of Khan, the officers of the starship Enterprise got a big uniform makeover. Gone were the primary colors of TOS and the dull gray pajamas of the first film. The new maroon uniforms gave Star Trek a new nautical-inspired feel that set the tone for a whole new direction in storytelling.
Worn by Kirk under his field jacket was a maroon vest. This is a prototype created by the film's costumers and includes a sewn in tag reading "Wm Shatner".