This object, known as a seal-die, is a metal mould from which the owner’s emblem can be imprinted in wax. This one belonged to Robert Fitzwalter, a powerful English baron heavily involved in forcing the English king, John, to agree to Magna Carta in 1215. It offers insights into the intrigues behind Magna Carta, into medieval notions of knighthood and chivalry and into social diversity in the Middle Ages.