I'm pretty certain it's a 16 bit card - old IBM credit card token ring card. But how do I confirm whether it is?

  

If it is a Cardbus card but the controller chipset does not support 32bit cardbus, then it probably will work through socket services. ISTR that cardbus can gracefully downgrade to 16bit, but that may be wrong.
Finally, if the chipset supports full 32bit cardbus services then it appears as a pci bus to the system, and cardbus cards (well, nic's at least) appear as pci cards.

As far as I can tell the Realport is a full cardbus services card. Socket services does not 'see' anything to do with the card itself. SS will report that the slot is in use but nothing else. That implies that it is more than just a point enabled card (althouhg it may be that
too). These cards among others will work with Veit's special programs, such as cbenable which I doubt a non-full-cardbus card would do.
    

But how do I identify the appropriate socket service driver?