This was the personal lightsaber of Jedi Council member, Master Plo Koon. He used it during during the many campaigns in the Clone Wars against the Confederacy of Independent Systems.
Koon used his lightsaber when went with Master Mace Windu and his assault team to rescue Master Obi-Wan Kenobi, his apprentice Anakin Skywalker, and Naboo Senator Padme Amidala from Geonosis. There he wielded it against the Separatist’s Droid Army.
Koon continued to wield his lightsaber when he became a Jedi General during the Clone Wars. He used to great effect from the battle of Abregado and and his rescue of Adi Gallia.