Single way 30A MEM ceramic fusebox.
The switch is shows here in the OFF position, and the plastic cover is secured with a single screw.
This would typically be used for a single higher power circuit such as that for an electric cooker, or possibly a small fusebox for lighting or a garage.
The two larger holes are for securing the switch to a wall or backboard.
Under the plastic shield, the incoming terminals are clearly visible below the switch.
The outgoing neutral terminal is located top right. The remains of the incoming wiring can be seen below and behind the device.
The fuse is a rewireable type, and has an asbestos flash pad in the centre. The fuse wire is missing, but would have been fixed between the screw terminals at each end of the fuse.