Custom House Tower

The building itself has no important loot inside aside from the normal items from containers.

Pristine Power Armor set

Like other Power Armors you can find in the map, this particular power armor is scaled to your level. So, to be able to get the pristine, fresh X-01 armor set, make sure you're at least LV30 above before "finding" it. Otherwise, you'll get an inferior power armor.

To start off, use the Custom House Tower as your starting point. From there, turn left (southwestward) and follow the road to the left. This will take you to the unmarked building called “35 Court”.

In the small room to the north you can access the Expert Terminal to turn off the protectron, turrets, and open the Advanced Safe beside it. Take the elevator to reach the top level of the building. Approach the security door in the middle to activate the two security doors on both sides containing a Sentry Bot and an Assaultron. Destroy them and hit the buttons found on the chambers where they came from to open the chamber containing the Power armor.