Sir Paton: allow - now you got me completely puzzled with
that schem!

the way I see it, is
(assumed the wire-cross between the 100k max feedbackresistor/22µ cap/100k trimpot/1M drive-pot
indeed is a node)
that DC-wise the 100kmax FB-resistor
does indeed establish an exact "Ub/2" bias at in- & output, as is taught in the schoolbooks,
which might be able to be pulled away from half supply either way by the 100k trimpot,
BUT: any AC signal to be fed back from the out- to the input through that "100k max" /and hence limit the maximum gain (A= R
FB/R
IN) is being shunted to ground by that 22µ capacitor before it gets combined with the inputsignal,
such that the circuit will always be working at its maximum possible physical gain (let`s assume 50 - 70 times), independant of the value of that FB-resistor,
and the actual amplification factor of the circuit isn`t being defined by the R
FB/R
IN ratio,
but only by the attenuation of the inputsignal through the 1M pot.
(err:
they say my posts are meaningless rubbish, lately, and ask why I do post here anyway, but this time I thought: what the heck - freedom of speech - let`s just try, write, and ask...

)
[(edit): hey: and congrats and welcome to the 5k
+ club!

]