This is a one gang polished chrome intermediate light switch fixed to a flat polished chrome switch plate.
It is manufactured in the UK by G&H Brassware. The switch has a white plastic surround. As it is an intermediate light switch it is used as the middle of three (or more) light switches within a circuit that is switching one light (or set of lights).
Please don't forget, you will need a 25mm back box to fit this plate.