This viewer box is the case only. It works perfectly fine. It has a lamp cord switch and I think the box is a phenolic or Bakelite product. When sold back then this box was mounted to a base and was used for primarily the education industry. The glass lens in the front is missing and is likely easily replaceable,1-3/4" diameter.  Holex made these units by hand, individually over a long period in the 70's. They went out of their way to use quality ingredients. The monochromatic filter inside is fine optics assisting in great viewing of these holograms in a dark room. I have some extra Holograms and I'll throw a few in for viewing.