The ornamental design for a putterhead, as shown and described.
FIG. 1 is a perspective view of a putter head as viewed from the front, top and one side thereof showing my new design; and
FIG. 2 is a perspective view of the putter head of FIG. 1;
FIG. 3 is a front elevation view of the putter head of FIG. 1;
FIG. 4 is a rear elevation view of the putter head of FIG. 1;
FIG. 5 is a side elevation view of one side of the putter head of FIG. 1;
FIG. 6 is a side elevation view of the other side of the putter head of FIG. 1;
FIG. 7 is a top plain view of the putter head of FIG. 1; and,
FIG. 8 is a bottom plain view of the putter head of FIG. 1.
The broken line showing of the rear portion of the wheel is included for the purpose of illustrating environment and forms no part of the claimed design.