Just like gummi said ...
I've never seen this before, Mac! Is this in the manual?
Thanks for posting this !
As it turned out, the thumb screw backed out very well.
I hit it with some heat (propane torch) and then drizzled on some Liquid Wrench which sweated in nicely.
The stainless "H Drive" set up from the OTG was a little persnickety due to built up crud I think.
I monkeyed with it, massaged it, held my mouth in various positions and then suddenly it made a "pop" as the control rod twisted out.
The H Dirive is the superior system IMHO.
Everything has been moved over to the Silver and the Silver is almost a Gold.
I'll need to fab a third handle and then it will be a Gold (wannabe).
Wannabe because it has the 3 wire triangle....the Gold triangle was kinda rusted.