The Leif Ericson was designed for AMT by Matt Jefferies, designer of the original Star Trek USS Enterprise and many of the ships that appeared in that series. The Leif Ericson never appeared in Star Trek, though it was used in a couple of Filmation's storyboards for the animated Star Trek series in the early 1970s.
The late 1960s through early 1970s saw three versions of the Leif Ericson:
The short story included with the Leif Ericson mentions that this kit was the first of several kits in AMT's "Strategic Space Command" series. This may have been an attempt by the 1960s AMT to start their own line of non-Star Trek spaceship models; in any case, only the Leif Ericson (and its alter ego, the UFO Mystery Ship) were produced.