This remarkable piece, made of solid gold, precious stones and pearls set in the obverse, once housed a relic of the Holy Cross, since the founder of the Portuguese nation, Dom Afonso Henriques, had dedicated the cult of the Canons Regular of St. Augustine to the invocation of the Cross of Christ.

The reverse is delicately engraved, presenting the Agnus Dei inside a lobed rosette in the centre: the lamb, the symbol of sacrifice and death, is, however, portrayed as standing, because it has been resuscitated. Depicted at the ends of the arms (in the shape of a fleur-de-lys) are the symbols of the four evangelists: the eagle of St. John, the lion of St. Mark, the bull of St. Luke, and the angel of St. Matthew.