This is a four gang flat black LED dimmer from G&H Brassware.
Each dimmer module/gang has a maximum of 120 watts. You can put up to 10 dimmable LED lamps or bulbs on each gang. They are push on/off dimmers. They are two way dimmer, meaning they can be used in conjunction with a two way light switch (not another dimmer).
Please don't forget, you will need a 35mm back box to fit this plate.