As promised here are some pictures I took with my cell-phone.
My God, it was 22 years ago when I bought this joystick...
9 pin din on cable's end that's for sure.
Original package only refers to it as 'Joystick' and the picture on it is slightly different (red joystick 'handle' *avoid censorship manoeuvre* and black sticker/white letters instead of orange joystick 'handle' *avoid censorship manoeuvre* and yellow sticker/black letters).
I was right, to use it with the spectrum it needed an adapter cable which I fortunately kept inside the box. Probably it is the same cable required for use with the other systems mentioned.
There are no instructions whatsoever apart from the information on top and sides of the package, although I don't think there are microswitches as the motion of stick and push of fire-buttons feels more like the old membrane type.
Well, I hope this sheds some light on this somewhat confusing joystick (at least to me)