Hi;
if you have the HP41 card reader (HP82104A) attached to an HP41, you can use the VER function and check the following:
for HP41 programs, they can be type A (all), D (data), P (program) or S (status). In this case, the card # is shown.
for HP67/97 ptrograms, VER returns type 7 (I´m not sure about other information, I think this is all)
The HP41 system does not read HP65 cards.
And you are correct: the HP71 and HP75 share the same cards. If I am not wrong, only HP75 standard program and data cards can be read in an HP71. Program cards from the HP71 that contain HP71-only functions not available in the HP75 will not work (the cards are read, data is loaded but generates error messages if handled). In some circumstances, HP71 cards can be used with an HP75. I know I tested some, but I did not went to an 'in-deep' research. Sorry!
Not much of a help, but may lead you to better experimentation.
Cheers.
Luiz (Brazil)