` ::No, I'm sorry, at least about the italian publication you are totally wrong, and I can understand that th situation is much more ``confusing for a non-Italian like you``:  Both ``Libro d'oro della Nobiltà Italiana`` and ``Annuario della Nobiltà Italiana`` are and ever was private publications. You are made a confusion whit the register kept in the former Consulta Araldica del Regno d'Italia, with the identical name of the first publication mentioned, it is the ``Libro d'oro della Nobiltà Italiana`` as well, but has never been published nor updated because was a manuscript register for internal use of the former ``Consulta Araldica del Regno``, the past Italian State bureau in charge of heraldic matters. After the fall of the Monarchy in Italy, and with the new Republican Consitution,  the ``Consulta Araldica del Regno`` has been closed (in force of the ``XIV disposizione transitoria della Costituzione Italiana`` that state ``La legge regola la soppressione della Consulta Araldica``). As a consequence, the ``Libro d'Oro`` manuscript register, ceased to be updated, (BTW!), and now stay in the ``Archivio Centrale dello Stato`` in Rome where anybody can ask for and see it, as you can check here in the Archive official site. I'm aware that recently, under the direction of the same ``Archivio Centrale dello Stato``, two volumes of the manuscript has been published in a ``faxsimile`` or ``photografic`` reproduction, by the same Archivio Centrale dello Stato. those are the details: ``Alle radici dell’identità nazionale. Prosopografie storiche italiane. Libro d’oro della nobiltà (I – II), sotto la direzione di Enrico Cuozzo e Guglielmo de‟ Giovanni – Centelles, con la presentazione del Sovrintendente Aldo G. Ricci, Roma, Società italiana di scienze ausiliarie della storia, 2009, pp. 291. cc.199,cc.199, ill. Riproduzione facsimilare per il 150° anniversario dell‟Unità d‟Italia, 1861 -2011.`` as you can check for yourself here, in the cited ``Archivio Centrale dello Stato`` official publications catalogue. Coming back on the two private publications, the ``private`` ``http://en.wikipedia.org/wiki/Libro_d%27Oro_della_Nobilta_Italiana Libro d'Oro della nobiltà Italiana]`` has been published and updated almost regularly (every 3-4 year, more or less) from more that a century, since 1910 to the present day (the most recent (24nd) edition was published in September 2010) by the publisher, the ``Collegio Araldico`` in Rome, an ancient and reputed institution (here the website. The second publication you mentioned, the ``Annuario della Nobiltà Italiana``, has been a totally  private publication too, founded in 1878 by `` Accademia Italiana d'Araldica``, an other reputed institution, and has been published almost regularly has well, but just until 1905, when the ``Accademia`` has been closed and the Annuario ceased definitely to be published (due of the founder death). After almost a century, in the year 2003, a small Italian publisher, the SAGI publishing House (here the website) established a new publication with the same title and same style, adding ``notables families`` and families not resident in Italy. This new Annuario della Nobiltà Italiana has been published irregularly every two or three years and the latest edition, the fourth of the new publication, dated 2007–2010. In Italy at the present, exists some more publication or ``Nobility register`` like the ``Libro d'oro`` and  the ``Annuario`` , all privately published as well, (BTW), they are the ``Elenco dei Titolati Italiani`` and the ``Albo d'oro delle Famiglie Nobili e notabili Italiana ed Europee``. Finally, about your assertion that this small italian ``Dukedom or Duchy`` of San Donato ``is not mentioned``, as for the evident confusion you made about the Italian ``peerage`` books, you should explain precisely at which publication you where referring to. I don't know if you are aware that all the Italian Nobiliary register are not conceiveid`` like the British Peerage, listing by TITLE, but by FAMILY, as a consequence, if you are searching for a specific title or  fief, you must firstly know the name of the family holders of the title. If can be of any interest of you, I cant assure that - about this ``Dukedom or Duchy``, for sure at least two of the cited publications, the ``Libro d'oro della Nobiltà italiana`` and the ``Elenco dei titolati italiani`` listed the families that hold the title, whit the only difference between the two that - due of the complex situation exposed above about the two titles enlisted to the two different lines of succession -   the ``Libro d'oro`` listed the first line of succession, and the ``Elenco dei Titolati`` listed the other line. I hope 