Please elaborate on what you mean by "the full server OS".
MS LanMan was Microsoft's networking OS of choice before NT. The base OS I believe was
based on MS OS/2 1.31.
Wiki has some more info:
en.wikipedia.org/wiki/LAN_Manager
I have a copy of it somewhere. Here is a picture of the package:
3.bp.blogspot.com/-KaapV596wY0/WLSlOaIjSJI/AAAAAAAAAdU/VNNQtD-iqjs7ZkvuQGqD…
-Ali