Action figure Major Matt Mason was an astronaut who lived and worked on the Moon and was introduced by Mattel in 1966.
The toy line included four astronaut characters sharing a common body molded of "Plastizol", a material also used in for example the "Thing Maker" line. The body was molded over a wire armature, and the head was separately attached. The removable helmet was actually based on early NASA space helmets.
Each character body was painted in a different color and had a separately modeled head.
There was also a three-story "space station" (moon base) and lunar surface and flying vehicles, accessories (powered by battery, springs, pneumatics, or strings). The designs of the early run of the accessories were based directly on concepts by NASA and the various contractors involved in America's "Race to the Moon" in the 1960s. The "Moon Suit" and the "Space Station", as well as the "Jet Pack" were actually seen as concept drawings in such magazines as "Look and Life". The laser weapons were copied from designs of science fiction shows of the time.
What's it worth? Take a look at this Major Matt Mason price guide: sold listings for a value indication.