From British Library website:
c 1260, This manuscript is one of three surviving exemplars containing the collected revised liturgy for the Dominican Order, produced at the convent of Saint-Jacques in Paris, following a period of reform and unification that took place during the mid-13th century. The two other surviving exemplars are now held in the general archives of the Dominican Order in Rome (Santa Sabina, MS XIV L 1) and the convent of San Esteban in Salamanca (MS SAL.-CL.01).
The volume was made in the early part of the 1260s for the personal use of Humbert of Romans (b. c. 1190-1200, d. 1277), the fifth Master General of the Order, and was probably taken with him on his travels to resolve any queries concerning the revised liturgy. It contains 12 of the 14 major liturgical books, lacking only the breviary and private missal, most likely on the grounds that Humbert would have had his own separate copies of these texts. A further two sections were subsequently added at the beginning and end of the volume (ff. 3r-22v, 572r-579v) during the 14th century. On the dating of the manuscript, and for a further description and discussion, see Giraud, 'The Production and Notation of Dominican Manuscripts in Thirteenth-Century Paris' (2013), pp. 122-39.
f. 2v: A list of the manuscript's contents.
ff. 23r-46v: Ordinal.
ff. 47r-80v: Martyrology.
ff. 81r-98v: Collectar.
ff. 98v-106v: Processional.
ff. 107r-140v: Psalter.
ff. 141r-248v: Lectionary.
ff. 249r-377v: Antiphoner.
ff. 378r-443v: Gradual.
ff. 444r-479v: Pulpitarium.
ff. 480r-525v: Missal.
ff. 526r-571v: Epistle and Gospel Lectionaries.
The manuscript contains a number of later additions:
ff. 3r-22r: Liturgical material, including proper Office items, Mass items and lections for feasts incorporated into the Dominican calendar between 1262 and 1357, added in a 14th-century hand.
ff. 572r-579v: Constitutiones of the Dominican Order (as they were between 1358 and 1363), added in a 14th-century hand.
Decoration: The decoration of the manuscript has been attributed to an artist of the Johannes Grusch Atelier, working with another from the Sainte-Chapelle Group, both based in Paris (see Branner, Manuscript Painting in Paris (1977), pp. 223, 237). The decoration accompanying the manuscript's 14th-century additions (ff. 3r-22v, 572r-579v) has been identified as the work of the Parisian artist Jaquet Maci (see Gousset, 'La décoration du ‘Prototype’' (2004), p. 53). Large and small foliate initials in colours and gold. Large puzzle initials in blue and gold, with red penwork decoration (ff. 3r-22r, 572r-579v). Small initials in blue with red penwork decoration, or red with blue penwork decoration. 'KL' initials in red and blue (ff. 47r-48r, 81r-82r). Paraph marks in red and blue. Running titles in blue and red display script. Rubrics. Underlinings in red. Marginal notes framed in red.
Square musical notation on a four-line stave in red ink throughout.