Lucas on-off toggle switch, part number 31780.
As used on a number of vehicles including:
- Aston Martins from 1977 to 1989
- Morgan 4/4 from 1969 to 1985
- Minis (Wipers), also Riley and Wolseley versions
Requires hole 14.5 mm diameter. Rated at 10 amps on 12 volt systems. Lucas 31780, BCA4293