In only one of the 39 surviving manuscript copies the letter also bears the closing legend Actum in castris in obsidione Luceriæ anno domini 1269º 8º die augusti ("Done in camp during the siege of Lucera, August 8, 1269"), which might indicate that Peregrinus was in the army of Charles, duke of Anjou and king of Sicily, who in 1269 laid siege to the city of Lucera. However, given that only one manuscript attests this, the evidence is weak. There is no indication of why Peter received the sobriquet Peregrinus (or "pilgrim"), but it suggests that he may have been either a pilgrim at one point or a crusader ; and the attack on Lucera of 1269 had been sanctioned as a crusade by the Pope. So Petrus Peregrinus may have served in that army.