There's good news and bad news I'm afraid Sam...
The good news is that I have
seen these before and had my hands on one. Last time was about 8 years ago, and it was
identical to the one you have. But there was no makers name, model, or serial number on
it. Not only that, but I also saw the identical model in the catalogue of one of the big
distributors. So it was still available and in production then. Don't be tempted to take
it apart, it's quite primitive inside. Quite a small coil, wound without any bobbin if
memory serves correct.
The bad news is that I can't find it in any of the old
lists I still have. My gut feeling is that it was either John Hornby Skewes or Stentor
that carried it. It definitely wasn't Pincotts, AllParts, or Aria...
But I am
pretty confident it was something made for one of the big distributors and probably made
in Eastern Europe for them by the look of the parts and construction.
When the going gets weird, the Weird turn Pro.