How to clean sliding power switch on HP21 Woodstock

[jupiters_spot]

Hi - just rediscovered these forums after a decade of having calculators packed away and it has rejuvenated my interest.

I have an HP21 with a dirty power switch: most times when I slide the switch to "On" nothing happens until I jiggle or press on the switch, and then the calculator works fine. Sometimes I can slide it to "On" and it just works without jiggling. I think I need to clean the contacts, but I can't seem to find a way to access the switch.

I open the calculator and remove the boards, separating the keypad from the logic board. The keypad "half" of it contains the power switch, but the switch is sandwiched between the printed circuit board and the plastic fascia. Those two appear to be held together physically by the plastic posts from the fascia that protrude through the PCB and appear to have been melted over. It looks like it was not intended to be disassembled.

Does anyone have guidance on how to access the innards of the switch?