The blank was designed by Master Richard de la Croix and is derived from a 1440 manuscript fragment. The blank shows a bastard Gothic hand which was very popular on the continent and in England in the fifteenth century.
I opted for classic red, blue and gold treatments. This excellent book given to me by my sister has been invaluable as a design reference, as it has many close-up pictures of extant manuscript pages in similar styles:
And here is my attempt. Unfortunately the colours really haven't shown up very well on the photos.
(Of course I can't show the name or device or it wouldn't be a surprise!)