With a bit of google translate help I see only one reference to the speed. iso 5, and that was qualified "Technique - kodak bellows without the viewfinder of the early twentieth century glass plates 6x9cm + EU2 iso ORWO not know how much but I think the 5"
These were originally for an electron microscope so perhaps looking at how one would use them for their intended purpose would give you an idea of how to use them alternatively.