Case for a wristwatch

FIG. 1 is a front view of my new and ornamental design for a case for a wristwatch;

FIG. 2 is a back view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a perspective view of the opened case for a wristwatch;

FIG. 8 is a perspective view of the closed case for a wristwatch;

FIG. 9 is a front view of the case for a wristwatch including a wristwatch shown for illustrative purposes only; and,

FIG. 10 is a perspective view of the opened case for a wristwatch including a wristwatch shown for illustrative purposes only.

The broken line showing of a wristwatch in FIGS. 9 and 10 is for illustrative purposes only and forms no part of the claimed design.