The Apollo Lunar Surface Experiments Package (ALSEP) was a set of experiments that were placed on the moon by the Apollo astronauts. The ALSEP received electrical power from heat produced by a radioactive substance. The power generator is called an RTG (Radioisotope Thermal Generator). The radioactive material used for fuel by the RTG was stored outside the Lunar Module, mounted in a casing like this one prior to transfer to the RTG.
This artifact was transferred to the Smithsonian in 1974 from NASA - Johnson Space Center.
Transferred from NASA, Johnson Space Center.