I am trying to understand if the 1961 Graduale Romanum and the 1961 Liber Usualis suggest Missa XV to be suggested specifically for Christmastide. When is it recommended to chant Missa XV (Dominator Deus) during Mass celebrated according to the Roman Missal of 1962 (the Traditional Latin Mass or usus antiquior)? I could interpret the text as "For Commemorations and Ferias of the Christmas season" in two ways:

1.) Missa XV could be sung for Masses of Commemorations only during the Christmas season and Ferias only during the Christmas season (e.g. the Commemoration of the Baptism of Our Lord Jesus Christ).

2.) Missa XV could be sung for all Commemorations throughout the year excepting the Mass of the Commemoration of the Faithful Departed (All Souls' Day) (e.g. the Commemoration of Saint Paul, Apostle) and on all Commemorations and Ferias of the Christmas season (e.g. the Commemoration of the Baptism of Our Lord Jesus Christ).