Hi Marc. Every good collection should have a skeletal S3. The switch is perfect as it is. There is no bakelite covering on it. You'll see why when you open the bottom as there is a hard leather part of the speed coil switch that insulates. You can see it below just peering out from beneath the switch.
The only pot metal on this fan is the gear box as far as I remember. The fan is definitely japanned.
This is a five speed fan but the issue with some of these speed coils is that sometimes, there isn't a lot of difference between the speeds. Be gentle around the speed numbers as you clean. Those are nice to have and hard rubbing will remove them. As I recall, one of our members produces a decal that will replace these numbers with Slow, 2, 3, 4 and Fast.
This fan's gears are a marvel of engineering and very clever. Remove the rear plate on the gear box and you will see this gear:
The two little ball bearings compress into the shaft so that the little lever (the one you say doesn't move) has a nub on the end of it that fits into the far right groove pushing the center gear on and off of these ball bearings which locks and unlocks the oscillation. The rotor looks like this:
The little lever appears on the far right of the picture below. You can see the nub on the end of it. As i recall, there is a set screw on the back of the gear case that must be removed to pull this lever up and out. That set screw fits into the center groove on that lever.
The press oiler on top of the gear case can be removed with a small open end box wrench for cleaning so that it will depress more easily (above picture far left).
The worm gear (below) can easily be removed so that you can slide the gears out of the rear case to clean them repack in red and tacky grease.
That center cog mechanism, allows the re-orientation of the fan's arc swing. You would move that while the fan is off. It controls where the arc begins and ends. Very clever design.
The stator comes out easily on these fans. Take care to label the wires so you know what wire goes where on the speed coil. I attach diagrams which you may find useful.
Hope this information is helpful to you, Marc. Congratulations on a nice acquisition!