It’s an old style meter to read the amount of electric you use. There should be a monitor somewhere it connects to via wireless. I have an “Owl” manufactured one.
The thing in the picture is now redundant. It's functions have been replaced by the smart meter and it's display.
My old Owl looked like this
https://uk.rs-online.com/web/p/energy-meters/8724666.
Does your black box in the pic open with batteries inside? Should do.