Hi
Moved into house 2 weeks ago. There is a switch inside next to the front
door for an outside light. It has a flap that slides down and has a rotary
dial with 0,2,4,6 and 8 around it and a turnable knob saying 'Early' one way
and 'Late' the other.

What is it and how does it work?. It has no manufacturer, part number or
instructions on it. The switch turns the light on/off whatever the settings.

Many thanks

SS