I have a manual, unfortunately it's in swedish and I don't have a scanner handy, either... My Durst looks exactly like yours. Is there something you want to know about it - maybe I can help you out?
BTW, the "extra lever" is the one on the left side on your photo. It's used to temporarily reset the filter changes you do with the three knobs - when you push the lever you get white, unfiltered light, which is basically grade 2 if you work with variable contrast papers. The "ND filter" you refer to is probably the red filter you have underneath the lens, which is used to shield the paper from being exposed.