FIG. 1 is an upper rear right 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 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 showing a portion of the top of the pen in FIGS. 1 and 5 are included for the purpose of illustrating environment and form no part of the claimed design.