napabar, I've been thinking about our discussion via PM, which centers on your use of the PowerBook G3 as the intermediary computer that links the 512k to the modern world. Would the software you run on the PowerBook work on an SE/30 running 7.5.5 or perhaps 8.1? I can run System 7.5.5 with the stock SE/30 ROM or OS 8.1 with a IIsi or IIfx ROM. My SE/30 has the means to connect to my Mac 512k via LocalTalk, plus the SE/30 also has Ethernet too. I was just wondering if an SE/30 would work, or if one really should use the PowerBook G3 you use.

Although I've never tried it, I do know of Apple LocalTalk Bridge, a 100% software solution that links LocalTalk computers over Ethernet, and it works on an SE/30. But I believe the protocol across LocalTalk Bridge is AppleTalk, which means it would not work to connect a Mac 512k with any flavor of OS X beyond 10.4.