The ornamental design for a wristwatchcase, as shown and described.
FIG. 1 is a front perspective view of a wristwatch case according to the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof; and,
FIG. 6 is a top plan view, the bottom plan view being a mirror image thereof.
The watch hands depicted by broken lines in FIGS. 1 and 2 have been shown for the purpose of illustrating portions of the wristwatch case that form no part of the claimed design.