The apparently unique iconography of the miniature above allows us to identify it as no. 26 in the 1898 Weigel and 1905 Hiersemann catalogues discussed in the previous posts:
The following item in the catalogue, no. 27, comes from the same manuscript:
|"Cette miniature est de la même écriture que celle du numéro précédent."|
One of the key pieces of evidence for this suggestion is the ex-Weigel cutting shown at the top of this post, now at the National Gallery of Art, Washington D.C.
Below the feet of Christ and a Virgin figure are kneeling four Dominican nuns, two Dominican friars, and (recognisable by the white cross on their shoulders) three Hospitallers:
Similarly, a cutting from the same series, sold at Christie's in 1991, shows the baptism flanked by a kneeling Dominican and Hospitaller:
Before the present identification of the two cuttings in the collection of Weigel (d. 1881), the earliest known provenance of any part of the manuscript was thirty years later, when one of the cuttings was sold at auction in 1911; it is now in the Wildenstein Collection at the Musée Marmottan:
But we can potentially take the provenance back all the way to the moment of its creation.
In the 1916 Jacques Rosenthal catalogue mentioned above, the cataloguer writes,
"Die Handschrift ist laut überlieferter Inschrift im Jahre 1300 von einem Mönch in Kaisheim vollendet worden."This information corresponds with a 19th-century inscription on the back of the Washington DC cutting:
"Von Anno 1300 aus einem Antiphonarium vom BruderInterestingly, the Weigel catalogue transcribes a somewhat different version of this inscription, in Latin:
Wernher von Eistetten Monch zu Kaisersheim”
"Anno Domini MCCC — conscriptum est a fratre wernhero de eisteten monacho cesariensi (Kaisersheim)."
It therefore seems that at the time of the writing of the Weigel catalogue in the late 19th century, the cutting was accompanied by a (medieval?) Latin inscription that has since been lost, except for its late 19th- and early 20th-century paraphrases in German.
It is not clear why a monk of the Cistercian abbey of Kaiserheim, in Bavaria, might write a manuscript for a nunnery in Zurich, about 260km to the south-west, but if the Latin inscription was derived from a genuine original colophon, the Weigel catalogue is potentially the only surviving evidence for the name of the scribe and the precise date of the manuscript -- which, as mentioned above, is been dated c.1300 on stylistic grounds in all the modern literature.
 Jacques Rosenthal, Catalogue LXXVI: Pergamentminiaturen des 12.-16. Jahrhunderts, Handzeichnungen des 15.-18. Jahrhunderts (Munich ), no. 3.
The date of this undated catalogue is given variously in library catalogues recorded in Worldcat, from "[1917?]" to "ca.1923". In fact it can confidently be dated 1916 from the fact that it was reviewed in the middle of that year in the monthly Zeitschrift für christliche Kunst, 26, no. 6 (digitized here).
Edit 6 January 2020:
Here is a link to the National Gallery of Art cutting, with a zoomable image.