Saw that when I was there 5 years ago. Some kind of magnetic mechanism and it looked very impressive if somewhat complex. I vaguely remember T de P telling me that a few were made but it was simply too expensive to produce as a commercial proposition. He's had a go at most audio things and I can understand his not trying tone-arms or cart's but rather surprised he never got round to tuners as they've complemented amplification for well over half a century. A valved tuner? There have been a few but not in the last 40 odd years, to my knowledge.