This is an OWL energy monitor which clips on to the mains cable and allows you to view your energy usage in real time. Sadly the receiver box appears to have stopped working, but I will throw it in too in case they just need linking together again. Or it may just need new batteries. Or both lol. You may be able to coax life from it.
Now we have a smart meter with display this isn't needed, although usefully it DID display outgoing power from solar panels, which the smart IHD doesnt. So MAy be of use to somebody? .

OWL energy meter ... sender only (St George BS5)