This unit is part of the Demonstration Advanced Avionics System (DAAS), a set of devices that was designed to test the feasibility of replacing classic aircraft instruments with digtial computing elements and displays. It was the forerunner of the modern "glass cockpit" now common to all new aircraft.
NASA transferred this to the Smithsonian in 1987.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.