Shifted fully to the Master of the Black Prayerbook, or a follower, gives us Walters Art Museum W.190. It’s another late 15th C Flemish Book of Hours, this one somewhat difficult to localize between Bruges and Liege. It’s been rebound out of order at some point in its life, but having the digitized copy allows us to return it to a more sensible, if not demonstrably original, order.

The calendar is complete “in intent if not in execution”. A scribal error caused April to only have 29 entries, and it appears the feast for April 19 has been omitted. The saints have a very strong Bruges character, often following the unusual saints of that city. There are a few on the wrong dates, and a pair of strange errors. May 23 has “Transfigura[o] d[omi]ni”, where that day is actually the feast of the Translation, which is an unusual feast peculier to Bruges. A stranger error is September 13(see f.9r below), usually the feast of St. Philip, is here listed as “Philippi & Jacobi”. That feast is May 1, and so points to a scribal error rather than a copying error.

(DB Id: 211)

With Walters Art Museum W.186 we are back to manuscripts from the circle of Willem Vrelant. This is a lovely book, the multiple illustrations of angelic musicians are rightly famous, with, as is sadly common, a rather undecorated calendar. There’s no illumination on the calendar except the KL at top, even the space for the more decorated ‘A’ in the dominical letters is unfilled. In the dominical letters there’s also a duplicate, the G for July 15 is written at the bottom of f.7r and the top of 7v.

The most interesting bit, however, is the beginning of the month of October(see f.10r below). The usual saint for October 1, Bishop Remigius of Reims, has been pushed to October 2. Listed on October 1, in red, are Sts. Bavo, an unusual but by no means unique saint for that day often seen in Dutch and Flemish manuscripts, and St. Gaidii. The catalogue interprets this as a variant of Aegydius, but the usual day him is September 1, and I’ve found no reference to a variant date of October 1. For now I am leaving this entry untagged, hopefully another example will come along and help clarify things

(DB Id: 209)

Continuing to add from the Walters Art Museum, W.183 is a late 15th C book from Bruges. The manuscript was illuminated in the circle of William Vrelant, as were Walters W.168, W.177, W.179, and W.180. The calendar is very sparse, both in terms of decoration and population. There is no border, Zodiac or labor of the month, only the bare minimum of KL at the start of the month. After the Calendar, there are lovely borders, with berries and birds, at the start of sections of the text and a profusion of full-page miniatures.
The calendar itself is rather common, about 50% full (155 saints) and of those about 1/3 high-importance feasts. There are a fair number of errors, even some of the important feasts, such as the Sunday of the Resurrection(should be March 27) or the Pope Leo the Great(should be April 11), have shifted by a day or two. I'd expect this is either scribal error in this MS, due to the low population of saints it's harder to keep registration, or an error in the source. Hopefully a larger DB of similar manuscripts will narrow the root cause.

(DB Id: 203)

The first of three Books of Hours added during a visit to the BPL manuscript collection last week, MS q. med 137 is a beautiful small Book illumiated in the Workshop of Willian Vrelant, with text in a semi-batarde script.  It's a somewhat unusual book liturgically, Use of Rome, but with calendar for Utrecht and text entirely in Latin.  Most of the Utrecht books are the Dutch transtlation of Geert Groote.  The Calendar itself has no very unusual details, there are only 160 entries and nearly all seem to match Bruges exemplars.  The image below(f.28r) is after the calendar, the start of the Mass of the Blessed Virgin Mary, showing the gray and blue foliage that is common throughout the book

Another one from the State Library of Victoria, in Melbourne Austrailia, RARES 09.R66HB is a slightly strange book.  The use of York is rare by itself, but in addition this one was written in Bruges.   The calendar is rather sparse 161 entries in total, and is missing some common feasts, such as the Christmas Vigil (Dec. 24).  An additional oddity is that the Octave of St. Laurence is listed (Aug 17), but not the actual feast, which would have been August 10th, see f.8r below