Which item was invented by a secretary and later sold for $47 million dollars?

Liquid paper, the common correction fluid was invented by Bette Nesmith Graham in the 1950s, she worked at Texas Bank as a secretary.

She would make mistakes often and became frustrated with not being able to correct the mistakes, so she came up with a way to correct these using white tempera paint and a watercolor brush.

Liquid paper would go on to be sold to Gillette for the sum of $47 million dollars in 1979.