Key layout as follows.
PUSH/PULL:
Right Hand Side:
(F#’/C#’) C#/Eb A/G Ab/Bb C#/Eb A/F (C”/D’)
(F/G’) C/B E/D G/F C/A E/B
(Bb’/Ab’) G/F# B/A D/C G/E B/F#
(Eb’/A) (D’/E’)
Left Hand Side:
E/F A/Bb C#/Eb A/G Ab/Bb (F#/C#)
C/G G/B C/D E/F G/A (Bb/C#’)
B/A D/F# G/A B/C D/E (F/Ab)
(C/C) same note – middle C
The keys in brackets are the extra keys (ie in addition to a 30 key instrument layout)
The ’ apostrophe indicates higher octave and ” the next octave.
I believe this is standard Wheatstone 40 key layout.