I have theses three strange goblets. I'm not sure what they are made of they kind of have a plastic feel to them. They are painted blue and white with a horse and carraige scene on the bottoms. Where some of the blue paint has chipped off it looks like an ugly brown translucent plastic? maybe bakelite? I didn't take pictures of the inside but it is not smooth. It has these four things that I guess are for reinforcement since they seem to brace the side to the bottom of the cup.
I think I remember seeing some documentary on PBS as a kid and part of it was about how some maker ended up with such an ugly colored product the only way to save his bussiness was to paint everything.