What is this odd little box I've been storing for years?

I received this switch/pot a few years ago with a used preamp and have never been able to identify it. When I asked the seller he said he didn't know either, he just thought it was part of the preamp (it's not). I wish I could post a picture here - but it's about a 3.5"black cube, with an older brown AC cord, an on/off rocker switch, fuse holder and small attenuator pot on the front. I though it might be a wireless remote switch for a turntable, but can't find any similar images online. Any ventured guesses would greatly helpful
Glenn