These AnSor switches are of a multi-tumbler design which allows them to be configured as 2 or 3 position with different contact configurations and either biased or stable action. They are quite sturdy but after many years corrosion can result in intermittent contacts which can't be cured reliably merely by the injection of cleaning fluid.
To dismantle the switch, first drill out the head of one end of the 3mm dia rocker pivot rivet and extract and retain the rivet. Remove the switch mounting springs and rocker exposing the heads of two further securing rivets. Drill these out and discard them. Remove the chromed plastic rocker housing and then carefully separate the tumblers and their support plate from the black plastic contact housing. The contacts, including the moving contact bars, are not plated and can now be polished with fine emery paper.
After cleaning and lubricating the tumbler slide, position it with the tumblers central (this can be somewhat tricky!) and re-engage them in the housing. Check that the mechanism is correctly located by activating the switch through the slot. Replace the rocker housing and secure the complete assembly temporarily with adhesive paper tape to prevent the springs causing everything to fly apart. Then bolt the assembly together with two M2 x 15mm countersunk-head screws and nuts replacing the discarded rivets (the heads should be inside the rocker housing). Now remove the paper tape, insert the rocker and replace its pivot rivet remembering the mounting springs. Tap the headless end of the rivet M2 and secure with another M2 x 15mm countersunk-head screw.
Test the switch. After cleaning the rocker apply white paint over the engraving and polish off the excess after the paint has dried.