This is a request for information from those learned in the Ambrosian Rite. I am myself profoundly ignorant in this area; the only traditional resource I possess is a reprint of the 1712 Ambrosian Missal.
The post-Conciliar, 1981, version of the Rite of Milan (and of a fair bit of Lombardy) contains a Eucharistic Prayer V and a Eucharistic Prayer VI. These are both (as far as I can see) non-Roman. They are said to date from the first millennium. They are ordered to be used, respectively, in Coena Domini and in Vigilia Paschali.
Some sections of these 1981 Prayers are found, mixed up with parts of the Roman Canon, in the 1712 Missal. I would like to know whether
(1) the mixed 1712 text of these Prayers is found in first-millennium versions of the Milanese Rite (mixed up with the Roman Canon as in the the 1712 Missal); with our conclusion being that the 1981 revisers had the bright idea of liberating these distinctively Ambrosian materials from the mixed forms of these canons; or whether
(2) there are extant first-millennium manuscripts with the texts of these prayers unmixed with the Roman Canon: implying that the 1981 reformers were simply and laudably returning to the evidenced early version of the Rite before it was Romanised.
The portions of the Prayers in the 1981 Missal which are found in 1712 are:
Maundy Thursday: para 77 tu nos participes ... primus offerri and para 81 Haec facimus ... tribuas ad salutem. [Spiritus sancti virtute is added, I presume in accordance with the predictable fads of the 1960s.]
Vigil: para 84 Vere sanctus ... liberaret a morte.
I wonder if the prelate who ordained Alcuin Reid uses the Ambrosian Rite ...