Break into a Dunedain guard post.
A captains cutlass (unique) or A plain sailors cutlass.
Kill everything in the guard post, take the key from the corpse of the resting guard and use it to break into the vault.
Sometimes A dunedain captain is wearing A suit of chain link mail which is a decent set of armour with has a built in helmet you can wear by using the following command.
raise coif
As A captains cutlass is unique, if it was not in then you will not get the quest point.
All of the npcs in this area cross protect, so it is worth attempting to focus them down to reduce the fight numbers.
If any of the information here is missing, or wrong, please let us know.