You may be interested in the history of this gizmo key. I related this to Alton McCanless (who copied a McDougall flute) and who now calls it after the inventor - the Hector Miller Gizmo :-
Years ago, when Ewen McDougall worked for the Flute Makers guild they got a guild flute in for overhaul and to their surprise they spotted this gizmo arrangement on it. It had not left their workshop like that.
It belonged to a Hector Miller, of Camden Town, Sussex, UK who is an
amateur flute player and a silversmith of national (UK) repute. He makes
jewelry for the UK Royal family and all sorts of people. Being a silversmith
of such quality he had the means and ability to do this modification to
his Guild Flute. The Guild thought it was marvellous and it was adopted
by Ewen and some
other Guild members as a standard method.
So, it was first invented and fitted by an amateur player as a modification to a British Flute Makers Guild flute.
Wessell flutes are another make with this feature.
This positioning of the key allows a much easier access to the key than in the "conventional" position
Photographed in the workshop of UK Flutemaker the late Ewen
McDougall of Ravensworth.
The above photograph and notes are as accurate as my knowledge of the subject permits
If anything above is factually incorrect, or if anyone can usefully improve or add to the above notes then please feel free to email me at john@fluteweb.net