Three separate rocker switches in one housing
One double pole and two single on/off
Colour White switches Black bezel
The three switches are interlocking
Looking at the switch as per the 1st photograph.
The master On Off double pole switch on the left can be thrown from Off to On independently, the next narrow switch when operated brings the 1st with it but can be returned on its own. The 3rd switch on the right throws all three switches when operated, it also can be returned on its own.
When all three are in the On position starting from the double On Off master on the left it can be returned and takes the other 2 with it.
In effect these were designed to control a heater, the master On Off switch would turn the unit on (maybe a flame effect would light up but no heaters) to turn either single or double heaters on the next 2 switches are used, and if the unit is turned off all three switches lock and all turn off.
60mm x 39mm cut out required
Snap in push fit to 1 -2mm thick panel
Connection via 8 x 6mm push on brass spade terminals ( could be soldered if required)
A copper linking strap links the double pole and the 2 singles