An old Wylex RCD.
The large metal terminals are completely exposed, and are a hazard, since even when switched off, the supply terminals would still be live.
30mA trip, maximum load 80A.
Part number WSES80/2 F. BS4293.
Even with cables installed, the hole in the cover is still big enough for fingers to fit through. The live terminals are just 5mm inside that large hacked hole.