The numbers on the cells would be focal lengths in cm. Maybe the sixth cell is a "flat" correction cell to be used with single cells? That could be why it has no number - no focal length?
The progression of numbers on the stops looks odd, but I think it could very well be hole diameter in mm. A simple measurement will confirm this.
I have a piece of cardboard which I pin to the wall at the end of a corridor. By focussing the image of the window at the other end of the corridor on the cardboard, I can read the focal length of the lens off a simple chart, calibrated with several modern lenses and a classic 15-25-35-45-55-65-75 casket set.