The A01.2 was the one of the combat outfits used by the Sith Order

Sith Order Organization Reconstituted Sith Empire

during and after the Great Galactic War

Great Galactic War Event Great Galactic War (3681BBY - 3653BBY)

.
The Sith Order was less regulated in its choice of armor and uniforms than the Imperial Army

Imperial Army (Sith Empire) Organization Reconstituted Sith Empire

, but to some extent its members were also required to wear a certain type of armor while on mission. This set of armor was provided to the warrior

Sith Warrior Miscellaneous Roles

's branch of the Order.