The ornamental design for a putterhead, as shown and described.
FIG. 1 is a front elevational view of the putter head;
FIG. 2 is a rear elevational view of the putter head of FIG. 1.
FIG. 3 is a left elevational view of the putter head of FIG. 1.
FIG. 4 is a right elevational view of the putter head of FIG. 1.
FIG. 5 is a top plan view of the putter head of FIG. 1.
FIG. 6 is a bottom plan view of the putter head of FIG. 1; and,
FIG. 7 is a front elevational view of a second embodiment of the putter head as disclosed in FIG. 1, the undisclosed the top, bottom, rear, left and right sides are identical to that disclosed in the first embodiment.