Dear Pierluigi,  I also have a Gavioli "Harmoniflute" monkey organ,
labeled:

  Harmoniflute a Trombone.
  Systeme Gavioli Brevete & Patented.
  14 Rue D'Aligre, Paris.

I believe it was built around 1855.  It has 38 notes in three
registers, and it plays eight tunes.  I have not seen a catalog entry
for this organ, but most reproduction catalogs are dated 1880 or later.

The most novel part of this organ is the "trombone", which is a cylinder
containing 3 reeds.  Internally it looks something like a 3-tone chime
whistle.

I would like to have pictures of your organ, if they are available.
What is the serial number of the organ (usually printed on the case
inside)?

Sincerely,
Marc Kaufman

 [ Marc kindly sent photos of his "Harmoniflute with Trombone" which
 [ I will place at http://mmd.foxtail.com/Pictures/  -- Robbie