The ornamental design for a wristwatch, as shown and described.
FIG. 1 is a first front perspective view of a wristwatch of the present invention;
FIG. 2 is a second front perspective view thereof;
FIG. 3 is a front elevation thereof;
FIG. 4 is a rear elevation thereof, omitting the unclaimed environment of a watchband solely for the sake of clarity of view;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a left side elevation view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a top view thereof; and,
FIG. 9 is a rear perspective view thereof.
The ornamental design which is claimed is shown in solid lines in the drawings. Any broken or phantom lines in the drawings are for illustrative purposes only and form no part of the claimed design.