Alex, I'll look for registration pins on the lower section of the bookform Sivoneg. My carrier was configured for slides and is charcoal in color.
BTW, all the odd named bits and pieces for the Durst 600 and 601 series make it harder to put together a system. It's a well designed, quality enlarger. Last night I reviewed Popular Photography (1973 - 75) looking for a product review. Could not find one.