The "hobby kits" Probert referred to was
AMT/Ertl model kit No. 6619 that was released within a year of the show's first airing. AMT, for whom Probert concurrently served as a consultant
[3], maintained close contact with the Art Department as their painting instructions proved to be highly accurate. A pre-production evaluation model was sent to the studio and ended up as display piece in various episodes (see below). How close this contact was, was evidenced by the fact that they unwittingly copied an in-joke one of the modelers performed on the studio model. Detailing the numerous panels onto the model was drawn-out and tedious work, and one of the modelers, no doubt in a mood of tediousness, arranged some of the panels to read "Ugly". Never discernible on screen, it was dutifully carried over onto AMT's instruction-sheet. (
Sci-Fi & Fantasy Models, issue 29, p. 54)