[planigan]

grayrabbit, are you sure that switch is missing a wafer? I see the wafer with the three terminals. Do you mean the rotating contact disk is missing?
If you can feel three positions click in when you rotate it, it should work.
When you say four position I take it that one position is off, second on, third one tone position and fourth second tone position. The wafer switch would really be a spdt switch. As you turn from off to on the wafer would turn but make no contact, next turn would make first contact on wafer and next turn would make second contact. I have not seen schematic but would guess switch places one cap in a curcuit and then either adds second cap or disconnects first and supstitutes second. Did you check for continuity between the three terminals on wafer? Wafer will not be electrically connected to on/off. Only physical connection of rotors on shaft between them. If you get continuity between one terminal and then one or both of the other terminals switch is OK. If ball bearing missing
(which gives switch the "click" and locking effect) you may be able to replce that. They are usually held in by tension of metal wiper. PL