Yes. Loosen the slotted screw half a turn or so then rotate the plate around so the face cam action pulls the pin outwards and disengages the bullwheel (gear) from the 3-step pulley. Then tighten the slotted screw again.
The plate you turn should have either a small knurled knob sticking out that you push on with a screwdriver to rotate the plate. Or there will just be a small hole in the plate if the knob has fallen out over the years.
You will see the plate has a slot in it that the screw sticks through. You rotate the plate so the slot moves all the way to one end or the other.
Once the plate has been rotated so the drive pin is pulled out, and slotted screw retightened, you should be able to spin the chuck or spindle without the 3-step pulley rotating if its held by hand. This means the direct drive is disconnected. Then you can swing the back gear into mesh with the two gears – the bullwheel gear and the small gear at the other end of the 3-step pulley.
Once you do that, you should be able to pull on the belts to rotate the 3-step pulley on the spindle and the spindle/chuck will rotate slowly. If it is all locked up, you have not disengaged the drive pin properly, so don't start the motor untill you can turn things over by hand first.