  We present an analysis of six 12 um selected Seyfert 2 galaxies that have
been reported to be unabsorbed in the X-ray. By comparing the luminosities of
these galaxies in the mid-IR (12um), optical ([O III]) and hard X-ray (2-10
keV), we show that they are all under-luminous in the 2-10 keV X-ray band. Four
of the objects exhibit X-ray spectra indicative of a hard excess, consistent
with a heavily obscured X-ray component and hence a hidden nucleus. In these
objects the softer X-rays may be dominated by a strong soft scattered continuum
or contamination from the host galaxy, which is responsible for the unabsorbed
X-ray spectra observed, and accounts for the anomalously low 2-10 keV X-ray
luminosity. We confirm this assertion in NGC4501 with a Chandra observation,
which shows hard X-ray emission coincident with the nucleus, consistent with
heavy absorption, and a number of contaminating softer sources which account
for the bulk of the softer emission. We point out that such 'Compton thick'
sources need not necessarily present iron Ka emission of high EW. An example in
our sample is IRASF01475-0740, which we know must host an obscured AGN as it
hosts a HBLR seen in scattered light (Tran 2003). The X-ray spectrum is
nonetheless relatively unobscured and the iron Ka line only moderate in
strength. These observations can be reconciled if the hidden nuclear emission
is dominated by transmitted, rather than reflected X-rays, which can then be
weak compared to the soft scattered light or galactic emission. Despite these
considerations, we conclude that NGC3147 & 3660 may intrinsically lack a BLR,
confirming the recent results of Bianchi et al. (2008) for NGC3147. Neither
X-ray spectrum shows signs of hidden hard emission and both sources exhibit
X-ray variability leading us to believe we are viewing the nucleus directly.
