The ornamental design for a putter head, as shown and described.
FIG. 1 is a top plan view of a putter head showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a top plan view of a second embodiment of the putter head as disclosed in FIG. 1;
FIG. 5 is a rear elevational view FIG. 4; and,
FIG. 6 is a left side elevational view of FIG. 4, the undisclosed opposite side being a mirror image.
The undisclosed sides of the first embodiment are identical to those disclosed in the second embodiment. The undisclosed sides in the second embodiment are identical to those disclosed in the first embodiment. The undisclosed bottom view forms not a part of the claimed design.