The old Cal Kit Manager 2.1 software, written by Barry Brown, who worked at HP (Agilent too?),
which works with 8753, 8720 and other early instruments, can read out the properties of the currently loaded calibration kit. It is on the GPIB menu, as "Read cal kit from VNA".
I'd like to do read this data in my own Unix software, but I can't find any documented commands to do this. I can find commands to set the parameters of a user kit (e.g C0 53.23 will set C0 of an open to be 53.23), but the C0 command does not support a query, so there's no C0?, so I can't see how this software reads C0, but it can read the complete cal kit.
Are there some undocumented GPIB commands to do this? Is there some trick to getting this information, which I myself have not worked out?