today also checked out the drive box that my friend had bought at the same state sale. That "A" drive can only seek one way, "B" drive seems to work. We didn't undertake any major corrective action today (especially as he doesn't have a computer to hook it to) just put it back together and made a mental note.
we also figured out that probably the disks he's interested in archiving (or at least inspecting) are double sided, which is incompatible with all our drives 😢
I've successfully copied disk images from my Xerox 820 to a Linux PC using some custom CP/M software!
I did it by writing a program in C(!) on my linux computer, transporting it over by xmodem, and then running it to transport the image data in a slightly customized ihex format over the serial port.