Maybe not the locals, but I would think most educated modern people, if they found the equipment, would have a large clue what was inside. There are not too many things you can put in a box on an isolated mountain top that would make it stay hot. It's not batteries, and it's not a engine.
In the late sixties, there were a dozen governments that would pay handsomely for such a box.
I wonder if they themselves knew about the risk involved.
This is a very sloppy and/or fear mongering article, e.g. when it talks about the device being 1/2 the size of the Hiroshima bomb, which was a uranium gun assembly design. It never points out you can't make this isotope of plutonium go boom, or the much fuzzier probability that a breach of the containment wouldn't likely cause a widespread contamination problem.
any scientists care to comment?