Ink container

 is a Quest Item found in the Arlington library media archive, usable in the Stealing Independence quest if you choose to give it to Button Gwinnett. This item cannot be dropped until quest is either completed or failed.

The room which contains the Ink Container looks heavily fortified due to all the barb wire and sandbags. The ink in question is in a metal box on a table towards the back of the room marked 'Restoration Supplies'.

Bugs
Bug: When picked up prior to talking to Button during Stealing Independence it will stay in your inventory forever blocking 1 weight even if it was "properly used".

Bug Fix: I accidentally found a fix for this bug, but I don't know which of the two ways fixed it. I disabled Button, basically killing him and then I took the real Declaration of Independence after unlocking the door with the password I obtained from his body.

Bug Fix2: In console: player.removeitem 3AA2 1 (PC version only)