This is a link to a copy of a Leica press release on the camera.

What follows is the shutter portion of that press release on the camera. I hope it helps, but if not I found the whole press release fascinating reading about the history.

"Shutter speed selection and manual film transport The shutter speed is controlled by selecting the slit width of a shutter curtain moving at constant speed. The engravings on the shutter speed button only indicate the slit width in millimetres, just like on the original historic camera. A slit width of 1 millimetre is equivalent to an exposure time of 1/1000 second. The fastest shutter speed of 1/500 second is obtained at the smallest slit width of 2 mm. The 5, 10, 20 and 50 mm slit width steps lead to exposure times of 1/200, 1/100, 1/50 and 1/20 seconds, respectively. The speed cannot be selected when the curtain is tight, but only while it is being tightened at a specially marked position of the rotating setting button.

"As the focal-plane shutter, unlike later Leica models, does not overlap when wound, a leather cap is put on the lens to stop light getting onto the film. “The moment the shutter is released is the climax of a whole chain of operations. The photographer is forced to capture the right moment, because he knows he will not be able to take the next exposure as soon as he likes. Concentrated photography leads to fewer, but very deliberate results“, as Daniel explains initial experience of working with the camera. "

This shouldn’t be hard for you. It sounds very much like large format today.

John Powers