The ornamental design for a pillbox, as shown and described.
FIG. 1 is a perspective view of a first embodiment of a pill box;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view of a second embodiment of the pillbox.
The broken lines shown in the figures form no part of the claimed design and the shaded lines in the figures show contour and not surface ornamentation. Except for the view shown in FIG. 8, all views of the second embodiment correspond to those of the first, and are therefore not duplicated.