Through an optical campaign performed at four telescopes located in the northern and the southern hemispheres, we obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/Burst Alert Telescope (BAT) and listed in the 54 month Palermo catalogue. All these objects also have observations taken with Swift/X-ray Telescope (XRT) or Chandra satellites, which allowed us to reduce the high-energy error box and pinpoint the most likely optical counterparts.