The anti-reverse is given tension by a small spring wire and catches in a notch on the inside of the drag wheel. The tension on the drag wheel is adjustable by the knob on the handle: slide it up and it catches on the highest indentation in the drag arm (i.e., moves the farthest before engagement) and provides the greatest drag; lower the button and it catches on progressively lower levels, resulting in progressively lower drag tension. there is also a set screw that can be tightened to hold the drag arm in even lighter positions to further loosen the drag.
All that was fairly straightforward, but it wasn't clear how to get into the drag to figure out how it was designed. there were two little screws in the brass plate in the center of the handle that looked to be holding the whole thing together. However, it turned out that those screws had been added later to further increase the drag by defeating the outer drag disk if the regular drag was too weak to hold...in other words, all those two little screws did was pin the outer of two drag discs against the inside of the drag cylinder...the whole thing was held together by a center screw, loosened by a two-pin "wrench" not unlike unscrewing a golf spike with a spike tool:
I cleaned it up and left off the little screws in the brass plate...works pretty nicely, although not quite the miiniature Kovalovsky Brian had envisioned
: 
Great job, JE, for deciphering what looked to me like a Rubiks Cube.
