Ancient Falmer Cuirass is a piece of unique light armor and part of the Ancient Falmer Armor set found in The Elder Scrolls V: Dawnguard.
Two versions of the cuirass with differences exist, similar to Steel Armor. The version worn by Knight-Paladin Gelebor doesn't include pauldrons while the one worn by Arch-Curate Vyrthur does.
The cuirass, along with the rest of the set, can only be obtained from the corpse of Arch-Curate Vyrthur after defeating him at the conclusion of Touching the Sky.
The cuirass can be upgraded with Refined Moonstone at a workbench, increasing the Base Armor rating by two points, the amount can be doubled if the Elven Smithing perk is unlocked.