Hello I've acquired a Rollei P11.0 slide projector - it's dual format with 35mm on one side and MF on the other and seems to me to have come from the same school of design as the Bismarck. The lens is a 110 - 160mm f3.5 zoom which focusses by remote control. I've worked out what most things do but one thing puzzles me. There is a large metal screw on the MF side where the slide tray sits which doesn't seem to do anything. Any idea what this does, or can someone point me towards a manual for the machine? Also can anyone please suggest a source of the MF slide trays, preferably in the UK? The 35mm side uses standard trays. Thanks.