Comment # 26 on bug 842844 from Dr. Werner Fink

Hmm ... indeed with

  /usr/share/man/man1/gnome-keyring-3.1.gz

and

  /usr/share/man/man1/gnome-keyring.1.gz

I'm able to read the .so link with man 2.6.6 and in the change log I found:

  * man-db 2.6.0 arranged to search the full manpath when expanding
    .so directives in manual pages (so that ".so name.1" works as well
    as ".so man1/name.1"), but this incorrectly did not take effect
    for manual pages that consist only of a .so directive.  This is
    now fixed.

... this is *new* as former the man had never done this ;)