The inventor, Martin Godfrey, was an architect. I think the device harks from the late 1980s. I have always been awed by the concept. But as time passes, I believe that there are parallel devices used in metal machining and that, perhaps, is where WoodRat is derived.
It doesn't matter. If you were to read all the online chatter (UK Workshops, SawmillCreek.org) concerning the machine you would learn two dominant themes ---- dovetail pins aren't accurate and the manual is confusing.
About the dovetail pins. As it turns out, the indexes for the Spiral Knobs are applied with a stick-down label. And they can vary from machine to machine. Also, poor quality control in manufacture leads to variances in the Button Setting. The button setting determines the shape of a Dovetail Pin.
As to the manual. Humphrey enjoyed an advantage in creating his Supplemental Manual. He didn't call it that. I do. Humphrey taught two classes of WoodRat instruction in Central England. So he benefited from listing to hundreds of owner students. He identified the hurdles to learning. The people at WoodRat didn't, and to the aggravation of many, they made excuses and kept insisting that WoodRat mastery is simple. The word "simple" is repeatedly used in the demo DVD.
Hell, life isn't simple. Martin Godfrey continued to assert that poor results in dovetailing were due to poor technique. Thus we now have the Router Boss. A competitor to the WoodRat. It addressed most of the shortcomings of the WoodRat and threw in a wonderful manual, greater workpiece capacity, built-in digital scales, improved dust collection, built in illumination. It is, all around, a much improved machine, and I would buy one if I didn't have more than $1000 invested in my WoodRat.
Oh, and the support offered by the Router Boss far exceeds that at WoodRat. Though I must say that I believe new competitor has spurred the WoodRat folks into action. New ideas and a new openness seem to be blossoming in England. When all is said and done, Martin Godfrey had a marvelous idea.