A pen wiper was used to remove the excess ink from the nib of a dip pen.
They could be simple or decorative, purchased or handmade.
Directions for making them could be found for children in An American Girls Book and A Girl’s Own Book as well as for adults in the pages of Godey’s Lady’s Book.
Handmade pen wipers came in all sorts of shapes from leaves to butterflies to animals. Some are all wool. Some are beaded. Tis is one page of my tablet folder:
You might be able to tell from the images I saved that i really like the animal kind. But, pen wipers originally caught my attention as I was assembling images and articles on doll projects.
This is an original pen wiper with two penny dolls I chanced upon when it was labeled as a pin cushion. This is the piece that inspired me to make the wax doll pen wiper.
Here are some of the pen wipers I’ve made in the last few months:
If I Had My Own Blue Box: 
Neat!! I never knew about these. Now I’m intrigued. Are they only for a certain time period or do they change over time? I am interested in what they might have looked like in the 18th century.
That is an excellent question. I’ve been looking at pieces from the 19th century. I will see if the are earlier ones.