This is a vernier rocket motor for the Surveyor unmanned lunar landing probe, America's first spacecraft to soft-land on the Moon. It provided small bursts of thrust for mid-course trajectory correction maneuvers and attitude and velocity control before and during the landing. It produced 30-104 pounds of thrust. For protection from solar radiation, exposed surfaces were coated with very thin gold plate.
The Reaction Motors Division of the Thiokol Chemical Corporation developed the vernier which was first used operationally on Suveyor 1 that soft-landed on the Moon in 1966. Five Surveyors out of seven launched were successfully landed on the Moon up to 1968.
The motor was donated to the Smithsonian by the Jet Propulsion Lab in 1970.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.