I always thought that the 4000PC came chronologically before the 4000SC, is 
this not the case?


For what it's worth, I've noted the chips around the CPU in my Olivetti M700-
10 which is supposed to be a close relative to the Magnum 4000PC.

LSI Logic
L1A7528
(C) MIPS 1992
32-00099
R4230
NAS 9250
WF36746 JAPAN <- this is the only difference

The memory controllers are about the same, just different last lines.

....maki....