The Excel Dynamic II is something of a mystery to me. It has the basic form of an Excel Dynamic - with its design and geometry a straight steal from the Huret Allvit. But then Excel seemed to get a sudden rush of blood to the head.
The Dynamic II has only one adjustment screw, and this effectively moves the whole body of the derailleur relative to the hanger. It has been suggested to me, by someone old enough to know, that the Dynamic II was designed to be paired with a heavily indexed lever - which effectively controlled the movement range. The single adjustment screw was for centring the derailleur in the style of a Shimano Positron derailleur. This is an interesting theory - but I have never actually seen the crucial lever.
Perhaps it was just a nonsensical design.