I had Art Cocchia, owner of Time Precision build me a couple rifles and 8 barrels back in about '95...... I had one of his rare earth neodymium magnet tuners installed in one of the stocks, sized for LV diameter. We spent a lot of time discussing tuners as I'd been goofing with them since about '85 as had he. Well, when the friggin' macaw wasn't squalling we talked, comparing thoughts.
But he was 'WAYYYY ahead of me! While he was on the phone he described the drawers of tuning devices he'd built, at that time he had over 100 prototypes up to 4 POUNDS in weight.....
That tuner in the pic could easily be one of his.... but I don't know.