This situation you encountered appears to be, from our testing results, an issue with the installer, not with your hardware. This situation occurs in all Macintosh models that have Token Ring cards installed, not just the PowerBook Duo in a docking station.
The "Easy Install" option of System Software 7.5.3 CD-ROM disc does not properly detect the presence of an Apple Token Ring card, hence does not install the necessary drivers. You must select "Custom Install" and then "Networking" and "TokenTalk" to get the drivers installed.