The Mignon AEG type writer

an optimized taping keyboard from 19th century.

Found in a museum in Salvador de Jujuy, Argentina.

This keyboard, the first known taping keyboard, is used by designating a character with a pendulum-like stylus, and pressing a separate key to enter the character. Notice that the layout seems already well optimized for this sort of entry, and that the system requires asymmetric bimanual input, the left hand acting as a selector and the right hand as a triggerer. 

Notice that the center letter is e, the immediately available keys following e are: ATONIDRG, which I presume are the most used letters in spanish, then the outer rows correspond to less used keys.

Space and new lines seem to be performed with the right hand, as well as key presses: the left hand seems to merely brush over the surface, selecting which is the next key to enter, while the right hand performs the actual key hits.

The mechanism is also remarkably simple. The pendulum drives a cylinder that is placed perpendicular to the paper roll. On the cylinder, the characters are layed out exactly like they are on the keyboard. Moving left or right controls a direct rotation of the cylinder, thereby aligning the current column on top of the paper. Moving toward or away from self produces the same effect on the printing cylinder, hereby aligning the current row with the current paper location.

Hitting a key with the right hand lowers the cylinder, hereby printing one character and advancing the paper roll to move on to the next character.

If you have a simple mean of computing the actual efficiency of this layout with respect to other layouts, I'd be interested to know the results. Most notably, I wonder if the layout of the outer rows is optimized as well so as to avoid crossing the center area as much as possible.