In the original version of the episode. Flint's home was depicted by a re-used matte painting of a Kalarcastle on Rigel VII from "The Cage". According to Star Trek Maps (page 28, chart D), Holberg 917G was the seventh planet in the system, and had once supported a neanderthaloid population similar to the Kalar. The single moon of the planet seen in the original version of the episode was named Tanisse.
The location of Holberg 917G on "The Explored Galaxy" star chart
Flint's home on Holberg 917G, as it appeared in the original episode