A famous art thief broke into a museum.

he is looking for a priceless gold medallion, however it is locked within a vault.
he manages to get into the vault but realized that the medallion is hidden within one of the five objects.
1-bomb
2-scissor
3-sword
4-knight
5-hourglass

there is an insciprtion that writes "silence is golden,three is the magic number"

amazingly the thief manages to take the medallion,what did he take?