Osterhagen Project

The Osterhagen Key was a device that was held by UNIT by the time of the New Dalek Empire's invasion of Earth.

After Earth fell to the Daleks, General Sanchez of UNIT gave the key to Martha Jones along with the prototype of Project Indigo to escape. Former Prime Minister Harriet Jones told Martha Jones not to use the key under any circumstances. (DW: The Stolen Earth)

The name was posibiliy derived either "Eastern City" or "Fossil City", depending on spelling. Also, "Osterhagen" is an anagram of "Earth's Gone"