Looking at Kusachian's small Japanese toys blog I realised that I had some of them!
Years ago I bought a bag of soft rubbery plastic space vehicles for fun. I've sent batches out over the years to friends. You may have got one or two! I blogged about them in 2012 here.
Unless I'm seeing things I reckon some of them are the same as these on Kusachian's site and ....... they fit together!
Looks like these are Omake or small premiums and came in that small box along with this leaflet depicting the full spaceship.
So what is it readers? What is this mysterious craft that I have soft parts to?