The ornamental design for a mirrored box, as shown and described.
FIG. 1 is a flat unfolded view of an ornamental design for a mirrored box;
FIG. 2 is an assembled front view thereof;
FIG. 3 is an assembled rear view thereof;
FIG. 4 is an assembled side view thereof;
FIG. 5 is an assembled top view thereof;
FIG. 6 is an assembled bottom view thereof; and,
FIG. 7 is a perspective view thereof.
The broken lines in FIG. 1 are fold lines illustrated in the other figures as solid lines when folded, and the broken line circles are for illustrative purposes only and form no part of the design.