This model of a Klingon D7 Battle Cruiser was used in the filming of the episodic television series "Star Trek," which aired on NBC from 1966-1969. The three-season episodic series is also known as the original series or TOS. In the original series, this is the standard fighter spacecraft of the warlike Klingon Empire. Although the lore of Human-Klingon history was later developed over additional television programs and feature films as well as novelizations and video games, Klingons first appeared in TOS toward the end of the first season ("Errand of Mercy"). This particular kind of Klingon Battle cruiser, the D7, first appeared on television in 1968, during the series' third season ("The Enterprise Incident").