Marblescopes derive their names because they use a marble instead of an object chamber. If you think about it and have studied basic math, you will discover that there are an infinite number of images which can be obtained from a simple marblescope. The image above and below are from the top instrument at the very bottom of this page.
The trick with marblescopes is to select suitable marbles. They must be mostly transparent and have flowing and swirling colored shapes of glass within them. Creating good marbles is a serious art form. Making pretty ones requires not only the proper tools but also skill and a certain amount of luck. You can spend an entire old-age pension check on one. These aren't the shooters you played "Keeps" with as a kid behind the schoolhouse.