Little Nell and her grandfather a going with the Punch and Judy playes to the races. The meet some other players, and Mr.Codlin, who is inside the miniature stage, speaks to a group they meet, from the opening (here called the proscenium) through which the puppets are seen when they perform. Here is a URL with pictures of Punch and Judy
portable theatres:
http://www.punchandjudy.com/harpers1.htm

What an excellent collection!

Anybody know these things as fit-ups?

Sometimes I deliberately make mistakes, to invite corrections. More often I goof, and pretend I did it on purpose. It later occurred to me, that the hinged flap that closes up the theatre, when folded down to show the puppets, makes the stage on which puppets declaim. That's the proscenium.