This dalmatic belongs to a set of vestments, composed of thirty four pieces, for use in the most magnificent high masses (the colour white was used in High Masses of Easter and Christmas). It was also used on the 24th June, the feast day of Saint John the Baptist, to whom the chapel is dedicated.
On such occasions, they would hung the splendid door hangings, put covers over the lecterns, the pulpit with the respective cover as well, plus a beautiful tapestry placed on the floor, covering it completely; on the altar a cushion for the missal, a veil over the chalice, and above this, the burse. If the Mass was presided by the patriarch, he would be wearing a main cope together with his very fine undergarments. He would be sitting on the faldstool, decorated with its rich embroidered covering, wearing buskins and liturgical sandals on his feet and gloves in his hands; on his head a mitre auriphrygiata, on his knees the gremial, on his shoulders a stole and on his arm the maniple, in such a way as if the whole person were wrapped in silk and gold. Around him his assistants: the deacon and sub-deacon, respectively with dalmatics and tunicle, each with a maniple and stole, and six serving canons dressed with copes.