I've seen people open them before; it's not that hard, especially if you're using a full-sized model. Bear in mind that in the '70s, there were probably fewer consumer safeguards in place so they may have been easier to open. But still, I don't imagine for a minute that it would take a great deal of effort to open a modern, full-sized model. If the goal was to preserve a piece of art on the glass, the simplest method to make it simpler would be to drill a few holes and drain out the aluminum dust.
On a side note, I'm at work. There are video monitors at my desk showing camera feeds. There's a roach trapped in one of the camera housings. Seeing a blurry, huge image of a roach as it walks over the lens is a little unsettling...but also kind of funny.