6-23 is a star system located in Federation space, home of the planet Marcus. This planet and system are in the area designated by Starfleet Intelligence as intelligence sector 2, and is in the vicinity of Starbase 19. (FASA RPG module: Star Fleet Intelligence Manual)
- This is one of only a very few stars in Star Trek to have purely numerical designation. It is possible this was shorthand for one of the other recording systems, meaning this star's full designation might be "UFC 6-23" or the like.