Bernard,
Interesting ! Have you never explored the origin and intended use of your air keys? They are in fact examples of an invention attached to James Alsepti according to a patent application 8th July 1885 No8290 in which two "relief valves" are described. In the tutor "The modern English Concertina method by Signor Alsepti" they are named "Bowing valves" in order to be used so that the bellows may be operated more analagous to "bowing" of the violin.
It is noteworthy in this context that Alsepti very strongly spoke against using the finger rests! :... "the pupil should never use the metal plates as a rest for that (fourth) finger". He also meant that each finger 1-4 should operate their corresponding rows 1-4 - which
is dubious in strict meaning since everyone can find that the hand (unless a child's) is wider than the 4 rows of the English keyboard.

So Bernard, why not use your fortune having such an instrument and become a complete master of the Alsepti school of playing?