hi! ok, i'm back at home again now, so i could inspect the keyboard more closely.
result:
it has the bars (sammelschienen), they're just on the inside... the older guy had them at the front. but the good thing is they're easily accessible by opening just 3 screws.
so i took a few photos. well they're quite nasty, i haven't cleaned it yet :-[
i hope now to be able to build me at least a kbd without velocity. maybe i could make use of the multitude of bars in some way... organ1.JPG organ2.JPG