I'd say it's an older Wemo light switch.

Useless without the powerstip that goes with it.

Pretty sure richms is correct.  It is a remote for a Belkin Conserve Switch.  Used to have one a long time ago, and was handy if you wanted to switch off all the power to something like an entertainment unit etc without reaching behind all the wires and all.

https://www.pcworld.co.nz/article/481360/review_belkin_conserve_switch/

Yann

Oh, and the remote is probably a paperweight now - I don't think it'll have any use without the power strip.  I don't think you can pair it with another device as far as I remember - though it might be possible if you could find a compatible strip (thought there are better options around these days).

If it‘s on 433MHz, one could try to re-use it with a tasmotized sonoff-RF.