The ornamental design for a pen, as shown and described.
FIG. 1 is a front elevational view of a pen showing my new design; the pen cover shown in FIG. 7 is not shown in this figure for convenience;
FIG. 2 is a rear elevational view thereof; the pen cover shown in FIG. 7 is not shown in this figure for convenience;
FIG. 3 is a left side view thereof; the pen cover shown in FIG. 7 is not shown in this figure for convenience;
FIG. 4 is a right side view thereof; the pen cover shown in FIG. 7 is not shown in this figure for convenience;
FIG. 5 is a top plan view thereof; the pen cover shown in FIG. 7 is not shown in this figure for convenience;
FIG. 6 is a bottom plan view thereof; the pen cover shown in FIG. 7 is not shown in this figure for convenience; and,
FIG. 7 is a perspective view of the pen with its cap detached; the pen cover into which the cap is inserted when the pen is not in use is shown in this figure.
The broken lines shown in FIG. 5 are included for the purpose of showing a portion of the pen that forms no part of the claimed design.