No, you are right I am not getting the answer because, unless I am missing something besides some cerebral matter, I can't imagine them to be cheese covers unless someone was a cheese fanatic. I did get a couple ideas, one person thought they could be small plant covers---they 9Tthe glass) come from a farming community and another thought they could be candy dish covers which makes some sense. As for chinese sex, someone came up with that too, but I think the great chairman discarded the devices after he in spoke in falsetto.
Glass goes beyond color, there is something that likes glass whether we know it or not, we can see through it, bend images, drink from it, make pictures and even have a glass of beer; and I vote that everyone, even the one's who are put off by my innocent inquirey, go to the cabinet, pick up a glass, pour some beer gently into it, watch the bubbles and enjoy the life that only glass can bring. Bottoms up!