Glen, I have the 12821 interface kit manual scanned, don't
appear to have the 9895A scanned. If you can't turn it up
anywhere else, I'll try to borrow a copy from Jeff Moffatt
or Frank McConnell.
The Amigo protocol is documented in Appendix A of
http://bitsavers.org/pdf/hp/disc/09134-90032-Aug-1983.pdf
Tim, if the floppy you were using was in a 10 1/2" box, it
was probably from a third party. Vertical mount drives were
made by Sykes, DSD, AED, and others.