Noticed this plug on my wall from when I moved into this house, and I just started wondering again about what it’s actually for. This is in the UK, if that helps. It’s on a big bulky box hanging on the wall below my desk next to two regular plug sockets.
Edit: best suggestion I’ve seen here is that it could be a fuse box for an alarm system. Makes sense since this house did have several security systems before I moved in. Also, for added context, this is in a bedroom and the wire coming out of it goes straight into the wall.
This panel has a distinctly UK look about it, and I was already thinking that before I read your confirmation. I think only the UK and Ireland use things that look even remotely like this. The rounded appearance also puts it post-war, pre-1980-something because everything changed to be more flat around that time.
As for its purpose, would a bathroom be at the other side of that wall, by any chance? Or was it at some point in the house’s history? Heated towel rail is a good bet, for example. You don’t want anything vaguely like an outlet in the bathroom (shaver sockets notwithstanding), so wall panels tend to go in a neighbouring hallway or room.
Note that some bathrooms have the light switch on the outside for similar reasons. Others have a pull cord inside the room, which is less able to cause electrocution.
(If you know of a bathroom with a regular light switch inside it, you’ve found a room that was once something other than a bathroom and whoever remodelled didn’t finish the job properly. Or maybe it’s in a very badly built house.)