  Through an optical campaign performed at 4 telescopes located in the northern
and the southern hemispheres, plus archival data from two on-line sky surveys,
we have obtained optical spectroscopy for 29 counterparts of unclassified or
poorly studied hard X-ray emitting objects detected with Swift/BAT and listed
in the 39 months Palermo catalogue. All these objects have also observations
taken with Swift/XRT or XMM-EPIC which not only allow us to pinpoint their
optical counterpart, but also to study their X-ray spectral properties (column
density, power law photon index and F2-10 keV flux). We find that 28 sources in
our sample are AGN; 7 are classified as type 1 while 21 are of type 2; the
remaining object is a galactic cataclysmic variable. Among our type 1 AGN, we
find 5 objects of intermediate Seyfert type (1.2-1.9) and one Narrow Line
Seyfert 1 galaxy; for 4 out of 7 sources, we have been able to estimate the
central black hole mass. Three of the type 2 AGN of our sample display optical
features typical of the LINER class and one is a likely Compton thick AGN. All
galaxies classified in this work are relatively nearby objects since their
redshifts lie in the range 0.008-0.075; the only galactic object found lies at
an estimated distance of 90 pc. We have also investigated the optical versus
X-ray emission ratio of the galaxies of our sample to test the AGN unified
model. For them, we have also compared the X-ray absorption (due to gas) with
the optical reddening (due to dust): we find that for most of our sources,
specifically those of type 1.9-2.0 the former is higher than the latter
confirming early results by Maiolino et al. (2001); this is possibly due to the
properties of dust in the circumnuclear obscuring torus of the AGN.
