Hansen Writing Ball - - Things Learned while reading "The Hound of the Baskervilles" - Sherlock Holmes

The keyboard of the writing ball

Hansen Writing Ball - Wikipedia, the free encyclopedia: 

experimented with different placements of the letters to achieve the fastest writing speed. Malling-Hansen placed the letters on short pistons that went directly through the ball and down to the paper. This, together with the placement of the letters so that the fastest writing fingers struck the most frequently used letters, made the Hansen Writing Ball the first typewriter to produce text substantially faster than a person could write by hand.

Writing ball - model from 1870

Writing ball - model from 1878