Thanks to those who replied.
I called my Open Storage Solutions tech. contact and he had the answer.
This is not the first time that he has been a saviour!
It turns out that the 8500c was not supported in the 2.3 release.
Add the following to your /kernel/st.conf file immediately below
the "target = 4 lun = 0" line, # /* Entry for Exabyte 8500C 8mm tape drive */
"EXABYTE EXB8500C", "Exabyte 8MM /w compression",
EXB8500C-data = 1,0x35,1024,0x0039,4,0x14,0x90,0x15,0x8c,3;
The devices supported are now;
8200 rst4 -> rmt/0lb
8200c rst12 -> rmt/0mb
8500 rst20 -> rmt/0hb
8500c rst28 -> rmt/0ub
Dept. of Astronomy phone: 519 661-2111 ext. 8697
Univ. of Western Ontario fax: 519 661-2009
London, ON, N6A 3K7