Zilog PDS 8000 Develpment System,

In my continuing efforts to catalog what I have, I ran across the Zilog PDS 8000 Model 15 Development System. It has dual 8" drives, is heavy :), and looks to be pretty well built. In checking the manuals I have against our "Big List", these Hardware Reference is copyright July 1979 while the dates in the list are 1983/1984. I see the model 11 listed but not the model 15 and the numbering scheme leads me to believe the Model 11 preceeded the Model 15. If so, the dates for the two machines seem to be conflicting. Does anyone have any more info? One other thing, the Hardware Reference title is "Z8000 Develpment Module, Hardware Reference Manual" rather than "Z8000 Development System" and I am *assuming* they are the same. The other manuals (Monitor listing, Linker, and Assembler) are dated from July 1979 through October 1980.