Ancient Shrouded Gear Obtained from the http://www.uesp.net/wiki/Skyrim:Locate_the_Assassin_of_Old quest.
The Ancient Shrouded Armor and Cowl have better stats then their normal counterparts, 100% poison resist instead of 50% and 35% more bow damage instead of 20% respectively.
The Boots seem to be the same, both affording the wearer 50% muffle.
I'm not so sure about the gloves though, as the verbiage in the descriptions is slightly different:
Shrouded Gloves - Backstab does double damage
Ancient Shrouded Gloves -Double sneak attack damage with one-handed weapons
Any thoughts?