FIG. 1 is an upper front left perspective view of a pen showing my new design;
FIG. 2 is a right side elevation view thereof, with the left side elevation view being a mirror image of the right side elevation view;
FIG. 3 is a rear elevation view thereof, with the front elevation view being a mirror image of the rear elevation view;
FIG. 4 is an enlarged top plan view thereof; and,
FIG. 5 is an enlarged bottom plan view thereof.
The broken lines shown in FIGS. 1 and 4 illustrate environmental subject matter and form no part of the claimed design.