Giotto, Back of The Stefaneschi Triptych
Tempera on wood
Pinacoteca Vaticana, Rome
The back and front of the triptych each have three main panels and a predella. Pictured here are the three main panels on the back. In the center Saint Peter presides from his throne holding the keys that are his attribute. On the corresponding panel on the front it is Christ who sits enthroned.
The saint standing on the left of the throne wears military garb and treads a small dragon with his right foot. Two military saints are associated with dragons: George and Theodore. George usually has a red-cross shield, so I would suggest that this is Theodore. His right hand rests on the shoulder of the donor, a bishop offering a book to Peter. Other bishops, with halos but without attributes that would identify them, stand on the right.
On the left panel are St. James the Greater, identified by the pilgrim's staff, and St. Paul, with his characteristic pointy beard and receding hairline. The latter holds a sword whose shaft has been broken in two.
On the right, St. Andrew is identified by the long cross and St. John the Evangelist is, as often, beardless holding a book and pen.
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See the front of the triptych, left panel: The Martyrdom of St. Peter.
See the front of the triptych, right panel: The Martyrdom of St. Paul.
Read more about St. James, St. Paul, St. Andrew, St. Peter, St. Theodore, and St. John the Evangelist
Photographed at the site by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.