Age indicators for GJ 504 compared to those of ι Hor and open clusters of well-determined age. In the various panels, GJ 504 is shown as a filled black circle, ι Hor as a filled blue square, members of the Pleiades open cluster as green filled squares, members of the Hyades open cluster as red circles, and members of the NGC 752 open cluster as orange filled squares. Upper left panel: rotation period vs. B−V. For GJ 504, both the literature rotation period (3.33 d) and the possible alternative period that is two times longer are plotted and connected by a solid line. Upper middle panel: vs. B−V. Upper right panel: log L_X/L_bol vs. B−V. In these plots, red filled triangles and green filled triangles represent the stars with X-ray upper limits members of Hyades and Pleiades, respectively. Lower left panel: lithium EW vs. B−V for GJ 504 (black square). Lower middle panel: U vs. V space velocities for GJ 504 and young moving groups (open circles). Overplotted are the boundaries of the kinematic space populated by young stars. Lower right panel: W vs. U space velocities for GJ 504 and young moving groups (open circles).