FIG. 1 is an upper front right perspective view of a pen showing my new design;
FIG. 2 is a left side elevation view thereof, with the right side elevation view being a mirror image of the left side elevation view;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is an enlarged top plan view thereof; and,
FIG. 6 is an enlarged bottom plan view thereof.
The broken lines around the inside surface in FIG. 5 are included for the purpose of illustrating a portion of the pen that forms no part of the claimed design.