Those are indeed very nice
It seems that the national military museum in the Netherlands that just reopend has some beautiful stuff as well. I still need to plan my visit.
Could you please send me a personal message (i can't send one to you, your acount is ristricted somehow).
Those at the Belgium museum are generally dated to 1450s, but i would date them to be somewhat more recent at 1490-1500s.
These canons do match as well and can be found at Harley Ms 4425 at page 139R (link, right top side you can select the page) http://www.bl.uk/manuscripts/Viewer..._ms_4425_fs001r
I wish i could show the picture here, but i am no longer allowed to use my trusted picture uploader... and i don't understand how i can upload pictures from my pc anymore, sorry about that.