This device served to lock the chair onto the rotator and gauge the chair's rotation when the unit was operating. This was part of the equipment for the Microgravity Vestibular Investigations experiments flown on Space Shuttle mission STS-42, the first International Microgravity Laboratory mission, in 1992.
NASA transferred the unit to the Musuem in 2004.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.