The ornamental design for a displaybox, substantially as shown and described.
FIG. 1 is a top perspective view of a display box showing my new design,
the end, side and bottom not shown being substantially the same in
appearance as the respective end, side and top shown;
FIG. 2 is a perspective view in a partially open position;
FIG. 3 is a perspective view in a further open position; and
FIG. 4 is a perspective view of the insert in a fully open position.