The hand-cranked duplicating machine was cheap. It didn’t require any training, and it made it easy for teachers to distribute worksheets and homework right in the classroom.

One design flaw: mimeographs were an inky mess. Like so much technology, the mimeo took a slow route to the classroom.  It was invented in 1887 by Thomas Edison, and was used in the early 1900s in offices and by publishers.

But it got it’s big boost during WWII, when it was used by the military to copy orders. Then it made its way into schools. And that whole slow tech thing kept it there long past its expiration date, when it should have been replaced by the copy machine.