In the St. Tikhon or Anglican Rite eucharist, what was composed during, and as a process of, the Protestant Reformation, was the entire anaphora or eucharistic canon. However, some texts from the pre-Schism Western Liturgy were retained, such as "The Lord be with you," and its response "And with thy spirit." The Lord's Prayer was, similarly, retained. And in the editing which was done to produce the first-ever St. Tikhon Liturgy (1979), even more portions of pre-Schism Liturgy were added, such as the Glory be to God on high (greater doxology). This much, covers the fixed texts of that service. There are also the changeable texts of that service, many of which were retained from the pre-Schism forms. Thus, on Easter Day, a St. Tikhon parish might sing at the introit the same text ("I am risen, and I am still with thee, alleluia," etc.) that they did in the year 950 in England.
In the Sarum Mass, as approved for use in the Russian Orthodox Church in Sept. 2008, 100% of the Mass texts date back to the West's Orthodox period (pre-1054). That statement covers the fixed texts of that service. Of the changeable or proper texts, it's about 98 or 99% from pre-Schism times, with a few proper texts from after 1054, such as the sequentia to the Holy Cross, "Laudes crucis attollamus," which is 12th century in origin. (A sequentia is a poetic and didactic composition for a notable feast, sung just before the Gospel reading while all the bells peal. They were done in the Roman rite from about 850 until about 1600, and a handful were retained even after 1600.
The Sarum Mass is simply the Roman rite, in the form which was most prevalent and typical across Western Europe, from before 1054 and up to the Protestant Reformation.
