Today marks the 50th anniversary of the first "Mass in Italian" to be ever celebrated, an event deemed important enough to be celebrated by the current Pope with a special commemorative Mass at the same church in Rome (Parrocchia di Ognissanti, Via Appia Nuova, 244) where it took place. The original Mass was celebrated by Paul VI on March 7, 1965 which happened to be that year's First Sunday of Lent. The repeatedly vandalized plaque now marking the event (see above) goes so far as to say that it was this event that inaugurated the liturgical reform decreed by Vatican II. (The text of the plaque says, "On March 7, 1965, His Holiness Paul VI, inaugurating the liturgical reform decreed by the Second Ecumenical Council of the Vatican, deigned to celebrate in this temple the first mass in Italian language, amidst the emotion and joy of an entire people, forever faithful and grateful.")
The rite used by Paul VI was the so-called "1965 Missal", essentially the 1962 Missal but with the modernizations and simplifications laid out in 1964 by Inter oecumenici, which document came into force on the same day as the Pope's Italian Mass. (We use inverted commas because there never was an editio typica for the entire Roman Missal as reformed in 1964-1965.) The actual Mass celebrated by Paul VI itself served as the inauguration of the "1965 Missal". It would not have been entirely in Italian because Inter oecumenici mandated that the Orations, Preface, and the silent priestly prayers including the Roman Canon (which continued to be said inaudibly) were to remain in Latin. It also ordered that "Missals to be used in the liturgy, however, shall contain besides the vernacular version the Latin text". Messa in Latino recently published a few pages from a 1965 Italian-Latin Missal showing the bilingual Ordo Missae. (In the USA, vernacularization was already being implemented as early as 1964. The US Bishops' November 1964 document with rules for the use of Latin and the vernacular can be read here.)
Nevertheless it is not true, as is sometimes implied in blogs oriented to the "Reform of the Reform", that the 1965 Missal only allowed a modest use of the vernacular. The permission for the use of the vernacular in Inter oecumenici is sweeping and includes all the parts said or sung by the congregation:
