You're correct. Only two wires coming out from the coil. Yesterday I tried to wind only 20 turns of wire directly to the magneto (put first some electrical tape to avoid cutting the insulation) and works OK too (spark less "bright", but consistent).

Third wire you can see in the picture (thicker black at right side of the picture) is soldered to the core of the stock magneto and must be connected to the engine body, in order to close the high voltage circuit.

I have not my camera today. I will try to upload another picture tomorrow.