PDP 11/05 S vs 11/05 NC

Just to change the subject.. There were "S" and an "NC" version of 11/05 high profile system. Why? I am curious if any DEC historians here know the reason for two versions of the same DEC PDP 11/05 *high profile* computer (not talking about the low profile). There are separate manuals for each type. The S seems to be more OEM-ish because it comes in an BA11-K chassis. I am guessing you'd see an 11/05 S as part of a larger system (PDP 10), whereas the NC model would be for a stand alone system. ??? This S's BA11-K chassis was used by other hardware by simply changing the backplane. The "NC" model chassis seems to be specifically for the 11/05 I don't think it appears anywhere else. If anyone is interested to see the different models I have a thread on my site for each type: 11/05 S http://vintagecomputer.net/browse_thread.cfm?id=622 11/05 NC http://vintagecomputer.net/browse_thread.cfm?id=249 ... and then there are the 11/10's.... -- Bill