The Oberlin Collage Libraries has facsimiles of illuminated manuscripts for student use; a few examples from the Art Library collection are listed here.
To find facsimiles enter the following keyword search in OBIS d:facsimiles and ([your keywords here]).
For example this OBIS search lists about 60.
For more about keyword searching see the Keyword Boolean guide.
The Hours of Jeanne d̓Evreux, Queen of France.
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Deutsche Malerei der Gotik
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Early Netherlandish painting
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Les Primitifs flamands: I, II and III