What I can tell you is the mechanical shutter speeds are B, and from 1/60 to 1/1000 second, and to use them them you just select them on the shutter speed dial. The mechanical shutter speed chosen will be shown on the left side of the finder. The indicator in the finder on the left should display whatever is chosen on the dial.
If I understand correctly, the shutter will not open at any mechanical speeds.
I would suppose there is something wrong with a linkage somewhere. It could be the dial is not transferring the setting to the mechanism. I suspect the camera was dismantled and something was not put back together right.