As reported by the Vatican Information System, February 20, 2012:

The great bronze throne encloses a wooden chair from the ninth century, which was long thought to be St. Peter’s own chair and was placed above this monumental altar because of its great symbolic value. It expresses the permanent presence of the Apostle in the Magisterium of his successors. St. Peter’s chair, we could say, is the throne of truth which takes its origin from Christ’s commission.

(extract from homily of 19 February 2012)

Steve Ray: “The ceremonial Chair of Peter in St. Peter’s Basilica. It is said that acacia wood of Peter’s 1st century chair is encased in this bronze memorial.” (I previously addressed the arguments in Steve’s pdf.)

– TurretinFan