GPO rotary telephone finger dials become sluggish over time, this is usually because of an accumulation of dust and perhaps over-lubrication in the past.
After cleaning away any residual dust, debris and old clogged lubricant, a drop of Britphone dial lubricant oil on the insides of the governor cup and on the governor worm drive should bring the dial mechanism back to its former glory.
Lubricating the governor cup will deal with noisy and slow dial returns, additionally a drop of oil on the central spindle will also aid slowness. For best results, ensure too that any residual debris is cleaned away from the dial centre spindle prior to application.
Britphone GPO Rotary Dial Lubricating Oil is a medium viscosity, high purity mineral oil, manufactured in the UK by Concept Oils. It is designed originally as watch lubricating oil, but is ideally suited for use with GPO rotary finger dials, each 10ml bottle will service several telephone dials provided it is deployed sparingly.
Appearance: Colourless liquid
Initial boiling point: >320C
Pour Point: -9C
Flash Point: >170C
Vapour pressure @20C: <0.1 k Pa
Relative density @15C: 0.853
Solubility in water: No
Viscosity @ 40C: 38.8cSt