Keys of Orthanc

The Keys of Orthanc were described as two great, black keys of an intricate shape, joined by a ring of steel.
During the rule of the early Stewards of Gondor, the Tower of Orthanc was locked and its keys were taken to Minas Tirith. The Steward Beren then gave them to Saruman in TA 2759 to act as Warden of the Tower on behalf of Gondor.
At one point during The Two Towers, Gandalf said to Saruman that if he handed over the Keys to Orthanc with his staff, he might soon be pardoned and receive both back. Saruman did not surrender them immediately, but did eventually, to Treebeard, who passed them to King Elessar.