Detecting exact position of a key is not a showstopper, I can remember that much (LOL) so I can test almost every key in shell like Save2600. Functional and 'special purpose' keys are left in doubt, how to provoke their respective feedback (currently I have no access to my working A500, just plain A500 with null-modem connected to PC).
I was hoping of some SW capable of capturing calls to intuition which should be enough for verification.