During an encounter with the IKS Gr'oth under the command of CaptainKoloth, one of the ships was disabled, and its cargo was transferred to the Enterprise. The Gr'oth later returned and attacked the second ship, disabling its propulsion systems as well. The ship was later recovered and towed by the Enterprise to Sherman's Planet. (TAS: "More Tribbles, More Troubles")
This appearance of the two robot grain ships was the first on-screen appearance of this ship class. The cargo drone ships were clearly intentionally labeled with the same NCC-G registry in the 1973 episode. It was not until later, when a cgi-model was created to represent independent starships in the remastered Star Trek in 2007, that ships of this class appeared with separate NCC registries.