DEC Keyboard LK401 has serial interface, 4800 Baud, 8N1. See more information on the keyboard hardware here. The keyboard is solid and heavy, has superb tactile keys and is of the old 80ies quality. That you simply cannot order on Amazon or so. For a long time, the keyboard was supported by the Linux kernel, but this time is gone. My idea: connect the keyboard to a microcontroller that can connect to a PC via USB.