As discovered by Mike Burrows, the LT-10 toy is based on a spaceship appearing in The Green Slime movie from 1968.
In a plot* that's very much a precursor to the 1998 Armageddon movie (starring Bruce Willis), the Green Slime tells the story of a team of astronauts sent out to intercept a meteor heading for a collision with Earth.
The Green Slime goes one better however, in that there's life on the asteroid (the green slime in question), which the astronauts unwittingly bring back to their space station and where it soon evolves into one-eyed, tentacled monsters.
The spaceship sadly doesn't appear in the film trailer
Shot in Japan by Kinji Fukasaku and starring Robert Horton, Richard Jaeckel and the lovely Luciana Paluzzi (my favourite bad Bond girl in "Thunderball"), the Green Slime is very much a B-movie. But it's got nice period hardware (presumably designed by art director Shinichi Eno) and it gave us a nice toy!
Notes:
*: I'm not revealing the entire plot; you might still want to watch this film (which should be found online with a bit of judicious digging).
If you don't mind spoilers, there's a nice write-up on Spectrum Culture and another, longer critique (with images) on Trailers from Hell (open in new windows). back to text
The spaceship that became LT 10 was also issued as a model kit by Midori in Japan.