The ornamental design for a registration box, as shown and described.
FIG. 1 is a top, front, right side perspective view of a registration box embodying my design, the dotted lines showing the position of a slot and a lock which do not form part of the design;
FIG. 2 is a top plan view of the design as shown in FIG. 1;
FIG. 3 is a front elevational view of the design as shown in FIG. 1;
FIG. 4 is a rear elevational view of the design as shown in FIG. 1; and,
FIG. 5 is a right side elevational view of the design as shown in FIG. 1, the left side elevational view being a mirror image thereof with the bottom view (unseen) being plain and unornamental.