Each shows a half-length prophet(?), looking upwards, next to an initial "I"; the palette and design of the initial "I"s are extremely like one another, so the main differences are the colours of the figures' beards and clothes.
The style of the cuttings is related to that of the Master of the Murano Gradual (of which some examples are in this blogpost), but is much more sculptural in appearance:
A number of other initials probably by the same (or a closely-related) illuminator have been published by Ágnes Tóvizi, "Some newly discovered Quattrocento illuminations in Székesfehérvár", Arte cristiana, 96 (2008), pp. 307-12, including this one:
The Yale Art Gallery website records no provenance for its cutting, except that it was donated by Robert Lehman.
In tracing the provenance of the Mortimer Brandt cutting, I discovered that it was one of a pair that were sold anonymously at Sotheby's, 11 December 1961; the Brandt one was lot 126:
Catalogue des dessins, aquarelles, gouaches anciens et modernes, ... , enluminures des 14e et 15e siècles, appartenant à Madame X... ... la vente aura lieu à Paris, Hôtel Drouot, ... 15 décembre 1934Neither the Brandt cutting nor the preceding lot in the 1961 Sotheby's catalogue are reproduced, but the description of lot 125 makes it sound identical, except for the colours of the prophet's clothes:
The 1961 Sotheby's cataloguer -- or, perhaps more likely, the person who consigned the two initials for sale -- knew that another cutting from the same manuscript had been sold eight years earlier, at the André Hachette sale in 1953, as lot 58 (although there would be no way to know this from the bland description, and there is no reproduction):
In summary, we now have:
- a description of a previously-overlooked sister cutting of the well-known Brandt and Yale cuttings
- traced the provenance of the Yale cutting to the important Hachette collection
- traced the provenance of all three cuttings to Paris
Edit, 28 Nov. 2020
Going through old papers I found a handlist of an exhibition at Sam Fogg's gallery, "Medieval Manuscripts: Fremch and Flemish Books of Hours & Miniatures from the Breslauer Collection and Other Sources", 15 March -- 16 April 2004, in which no. 1 was this:
(The poor image of the iamge is due to the fact that it is an enlarged photo of an inkjet printout, in which the image was about 35×20mm).
EDIT 7 Jan 2021
I now realise that the Fogg cutting above is in the Breslauer exh. cat. by Voelkle & Wieck, 1992, no. 76. With a better image, it is now apparent that, while the composition is very similar, the style is different (though still attributed to Venice or the Veneto) and the Breslauer one is attributed to Cristoforo Cortese: