One of my favorite precious miters is this mitra pretiosa, depicting what appears to be the Assumption of Our Lady in the center. The miter displays rich embroidery with gold and silver thread, studded with precious stones, jewels, pearls, and gems. The infulae end in gold fringes. The miter I have been told was a gift to Montini by Pius XII on the occasion of his nomination as Archbishop of Milan. Such a work of art to behold.
Customarily the precious miter is worn on more solemn feasts and generally whenever the Te Deum is sung in office or when the Gloria in Excelsis Deo is sung in the Mass. It is used from the beginning of the Mass until the Introit, then the gold cloth miter, until the Credo inclusively. Finally, the precious miter is used until the end of the Mass. It is also worn going to the church and returning. And at the washing of the hands, for the incensation, and in giving the solemn blessing at the conclusion of sung Mass. The precious miter is not worn during penitential times such as during Lent and Advent (except on Gaudete and Laetare Sunday).
Further information on the history of this miter is unknown to the author. It is kept in the Tesoro della Basilica Vaticana (not part of the Sagrestia Pontificia), under the care of the Rev. Fabbrica di San Pietro, managed by a delegate who is a bishop.
If readers have any additional info, please feel free to reach out. Because today it is kept in the Treasury of St. Peter's (closed to the public), few privileged visitors catch a glimpse on a special VIP tour (students of sacred liturgy at Sant'Anselmo have been known to visit in the past on a private tour).
Montini wore the miter both as Archbishop of Milan as well as several times as Pope. Below he is seen as a Cardinal wearing it at the Corpus Domini procession in the Ambrosian See of Milan.
