Not sure where I got this from: But may be of Interest.
Controls. (See Sketch 15029.)
20. The moving parts are all controlled from the eyepiece position. They are indicated diagrammatically on Drawing 15029.
Focus adjustment by rotating eyepiece "A."
Elevation and depression by moving the lever "B."
Raising and lowering the periscope by means of the lever "C."
A dial "C" indicates the position of the elevation, extremes on the dial being 9.3 and 14.6 metres.
A separate handle is provided apart from the periscope for raising and lowering the periscope is desired.
Bearing scale situated at "F." Bearing is also indicated on dials "E," where an adjustment is provided so that the dials can be set at any desired constant difference from the true bearing.
Change of magnification controlled by the lever "G."
Colour glasses inserted by the lever "H."
The periscope does not embody a range estimator.