Walked nearby. I could not find any buildings with signs on them mentioning these "N200"-ish codes. There are however many streetside signs with a map of the campus, and the maps label the buildings this way. Every building has such a code, but some are also known by a normal name, so I think the ref=* tag is more correct for these.

I'll try to remember next time I visit to photograph one of the signs, so I can edit all of these into ref=*s directly from the primary source.