X-no-Archive:yes
Joe Geiser supplied 'the missing piece'. We are running SAMBA 1.9.16p9.
SAMBA did not recognize UNCs until 1.9.18. Mapping a drive to the share,
which I normally never do, allows the customization to be seen when viewing
the share as a web page, thus sharing the custom description of the share
and the link to a web page (under Apache/iX, of course) with our users.
So, it can be done.