If it was me and I didn't have a service manual explaining this- Put that pin on the bottom of the shutter speed dial so that it is closest to the prism. When I look in the circular slot on the body that the pin will ride in, looks as if there is a piece of metal that intrudes into the slot more and more as you head 'right' in your photo (towards the right end of the camera). Take a small screwdriver to see if that piece of metal can be pushed to the outer edge- gently. I wonder if that is the speed control- the piece of metal connects to a resistor or such, and as the pin on the dial moves left to right, the metal is pushed away, leading to a change in the circuit.
Looking again, it could be that the small circular tab on the bottom of the shutter dial goes int othe cutout in the metal circle on the body and the whole metal dial rotates as the shutter dial moves?
Well, that's my guess. Maybe I am not seeing something since I only have photos, not the actual camera. Look at the interaction of the pin and the slot and see how it 'wants' to go together?