The base is white ceramic, the front is a brown hard plastic material.
This example is unused and still in the original box. Note the 'C' moulded into the end of the switch lever.
The black spots are a filler which has been applied over the metal screws that hold the switch components in place.
The holes left and right are for woodscrews to fix the switch to a woodn pattress. These would be installed from the front, after removing the brown plastic cover.
Made in England, and 'New Pattern'.