Plot boards such as this one could be used by Gemini astronauts to store and work on star charts or maps of the Earth, the latter with tracking stations and landing zones marked.
NASA transferred this object to the Smithsonian in 1968 as a part of a large shipment of items from the Gemini spacecraft manufacturer McDonnell Aircraft in St. Louis.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.