Richard Erlacher stated as follows:
  Joseph Kaye sprach thusly:
  I got an Altos 586 from a friend a while ago,
with an external 2400 baud
 modem and a Wyse (50?) terminal.   There were no Unix install disks
 included.  I am looking to reinstall the OS, does anyone know where I
 could get a copy of the Xenix that it uses? 
 Are you sure it uses XENIX?  I gave one of these to Will Jennings, along 
with
  the companion tape drive, a couple of years back.
Perhaps he can help you.  
There were Altos' that ran MP/M-II, and others than ran XENIX... ISTR
that the 586 was the squarish-box that ran MP/M-II, while the other
model that had a hi-techish, Datageneralish look to it ran XENIX.
We had both...
Regards,
-dq