Good points, as usual, Denny.
Yes, I think it was called a piston jack, but perhaps not a hydraulic-driven piston - screw-driven is most likely the correct terminology.
The heights given in the spec manuals are the heights of the jack at fully extended and at fully closed piston. It is interesting to note that the dimensions for the 3100 jack are the same for all Advance-Design years (I am not certain if all characteristics of the 3100 jack-handle/wrench are the same for all years).
