The ornamental design for a casing for a powerlock, as shown and described.
FIG. 1 is a perspective view from above and to the rear of one end and the
interior of a casing for a power lock showing my new design;
FIG. 2 is an end elevational view thereof;
FIG. 3 is a plan view of the casing taken from a position opposite to that
shown in FIG. 4;
FIG. 4 is a plan view of the casing interior; and
FIG. 5 is a perspective view (a) of the casing bottom taken from a position
opposite to that shown in FIG. 1, and (b) of the end of the casing
opposite to that shown in FIG. 1.