The black reverse color lower octave of keys on both manuals are actually presets. By depressing one of these notes, they key will stay down, causing the organ to play the labeled stops such as Dulciana, French Horn, Swell Diapason etc.
The B flat & B (marked Adjust at least on one in the photograph here) are adjustable via the drawbars. On the CV there are two sets of drawbars for each manual playable by each of these adjustable presets.
