As a form of address, "Monsignor" is not itself an appointment (properly speaking, one cannot be "made a monsignor" nor can one be "the monsignor of a parish"). Its use is connected with honorary titles. The three titles most often seen in connection with the style "monsignor" are Protonotary Apostolic, Prelate of Honour, and Chaplain of His Holiness. These honours are bestowed upon a priest by the Pope, most often through the instrumentality of the local bishop.
A protonotary apostolic is a member or honorary member of the Roman Curia. In ancient Rome there were seven regional notaries. With the development of the papal administration, these seven became the palace notaries of the papal chancery. In the Middle Ages the protonotaries were very high papal officials, often raised directly from this office to the cardinalate, but their importance gradually diminished.
Since the sixteenth century the popes had appointed honorary and titular protonotaries. On 8 February, 1838, Pope Gregory XVI re-established the college of real protonotaries with seven members called protonotarii de numero participantium or numerary protonotaries. They were known as participating protonotaries because they shared in the revenues of the Roman Chancery. Pope Pius X legislated four classes of protonotary in 1905, three of which were purely honorary designations. A protonotary apostolic was entitled to wear the vestments of a bishop ("pontificals") under certain circumstances.
After these reforms, Apostolic Protonotaries were classified either de numere or supernumerary. Chamberlains and chaplains have been grouped together as chaplains, a specifically priestly-sounding category. Papal Chamberlains used to be appointed only for the lifetime of the Pope, so that the appointment had to be obtained anew from his successor. Whether this distinction remains for chaplains is disputed.
As a result Monsignori are now classed into the following three ranks, in descending order of precedence:
One year later, an Instruction of the Secretariat of State simplified the dress and the forms of address. Papal Chamberlains were formerly called "Very Reverend Monsignor" and the higher ranks "Right Reverend Monsignor". In the reform this was simplified to prescribe for all the form "Reverend Monsignor", often reduced simply to "Monsignor". Only the Apostolic Protonotaries de numero were styled "Most Reverend Monsignor," the same style as when addressing bishops.
The dress of Monsignori was also simplified.
The numerary protonotaries continue the work of the College of Protonotaries and still perform certain duties with regard to papal documents. A number of other superior prelates of the Roman Curia are also treated equivalent to apostolic protonotaries de numero, if they are not also bishops. These include the auditors of the Sacred Roman Rota, the four clerics of the Apostolic Camera, and a few others. Together, this group of clergy are called the prelati di mantelletta or prelates of the mantelletta because of their distinctive attire.
Laymen holding a post equivalent to "Papal Chamberlain" today are styled "Gentlemen of His Holiness" and wear a golden chain or collar similar to that worn by the previous papal chamberlains.
The only privileges of dress that Pope Pius X granted them were a black silk fringed sash, black piping on the biretta with a black tuft, and a black mantelletta. As a result of this they were in some countries referred to as "black protonotaries. However, "Pontificalis domus" of Paul VI removed this position from the Pontifical Household, even though the title of "monsignor", which is to be distinguished from a prelatial rank, has not been withdrawn from vicars general, as can be seen, for instance, from the placing of the abbreviated title "Mons." before the name of every member of the secular (diocesan) clergy listed as a vicar general in the Annuario Pontificio. (Honorary titles such as that of "Monsignor" are not considered appropriate for religious.)
The Secretariat of State has set minimum qualifications of age and priesthood for the appointment of Chaplains of His Holiness (35 years of age and 10 of priesthood), Honorary Prelates (45 of age and 15 of priesthood) and Protonotaries Apostolic Supernumerary (55 of age and 20 of priesthood). However, it waives the minimum age limit for vicars general and judicial vicars proposed for appointment as Honorary Prelates, in view of the fact that, as long as they hold the office of vicar general or judicial vicar, they also hold the still higher rank of Protonotary Apostolic Supernumerary. For the same reason, the Secretariat of State does not consider it appropriate that someone who is already a vicar general or judicial vicar be appointed only a Chaplain of His Holiness.