I claim the ornamental design for a military service headstone medallion, as shown and described.
FIG. 1 is a top view of a military service headstone medallion showing my new design; and,
FIG. 2 is a side view thereof, the undisclosed rear does not form part of the claimed design. The broken lines in FIG. 2 are for illustrative purposes only and do not form part of the claimed design.
The insignia on the medallion forming part of the claimed design is a registered trademark of the U.S. Department of the Navy, 1322 Patterson Street SE, Suite 300, Washington Navy Yard, Washington, D.C. 20374-5066.