His dog tags.

His dogtags are covered in scratches, general wear and tear, but the two most important markings are:
   /                                   \
 /              O Po/s              \<-------- Lily's claws; secondary break-away tag
|            0000/0000    \      |
|           DEL/ANEY          \    |
|                 TD                   \   | <------ Sebastian with knife; main tag
 \              JEW                  \  /
  \                                       /