Orbimetrix Planetary Slide Rule

The thing that appeals to me about this wheel is the clear plastic arm that rotates around it. I don't know why I like it. One is allowed to entertain foolish fancies, isn't one?

This wheel is 6.75 inches across, exclusive of the arm. The copyright date was 1970. It's made of a sturdy plastic and is perfectly usable. What you use it for is beyond me. What do I look like -- an astronomer?