The ornamental design for a stringed musical instrumentheadstock, as shown and described.
FIG. 1 is a perspective view of the stringed musical instrument headstock;
FIG. 2 is a front elevation view of the stringed musical instrument headstock of FIG. 1;
FIG. 3 is a right elevation view of the stringed musical instrument headstock of FIG. 1;
FIG. 4 is a top plan view of the stringed musical instrument headstock of FIG. 1;
FIG. 5 is a left elevation view of the stringed musical instrument headstock of FIG. 1, opposite the side shown in FIG. 3;
FIG. 6 is a rear elevation view of the stringed musical instrument headstock of FIG. 1; and,
FIG. 7 is a bottom plan view of the stringed musical instrument headstock of FIG. 1.
The broken lines shown throughout the views are included for the purpose of illustrating environmental structure and form no part of the claimed design.