If you've bought the limited Brass-top version you'll need metal polish and a rat-tail file or Dremel to tidy up the nixie cutouts - make sure they are clear before fitting as some nixies can be a tight fit.
Carefully sand the case top and bottom making sure not to scratch them, the side rings will be hidden so scratches aren't so much of a problem but the are fragile so don't put too much pressure on them.