@tubetime The ST-412 has an NCR 6500/1. This was also used in the Amiga keyboard controller.

There's a schematic floating around from the Amiga ppl for a circuit which dumps out a 6500/1's internal ROM. I still have the 6500/1 off my dead ST-412, but haven't gotten around to making the dumper yet.

Wonder if a similar circuit could be used for R6518...