Thanks to Suzy Richards we now have the supplementary pages from the manual of the Essex Mark II 35 mm tank. The manual is identical to the Mark I with the addition of these supplementary pages.
The supplement describes operation of the tank with Leica Type B labyrinthine film cassettes which have to be opened before the film can be withdrawn. Unlike the Rondinax 35U, the special Zeiss Contax cassettes cannot be used in the Essex.
For users of modern standard cassettes the presence of the left-hand knob on the Essex Mark II, just as on the Rondinax 35U, can be completely ignored. How many users of the old Leica and Contax cassettes are there now?