The attachments are images of a small variable cap from a Heathkit
DX-40. The cap was sprayed with Deoxit and washed in warm soap & water
before spend four minutes in an ultrasonic cleaner.

drive_cap.jpg - capacitor as found in circuit
after_1.jpg - shows pitting on plates
after_2.jpg - side view looks good

This was just an experiment. An exact replacement for the capacitor
was on-hand and has been installed in the transmitter.