Monroe Adding Calculator from Colorado. Motor attached on left side. Column zero buttons are in red. Left-right shift crank in front, Counter and sum reset crank on right. (High Speed is relative - multiplication takes a few seconds). There is a manual override knob on the right side (not pictured) for advancing or resetting in case it gets stuck mid-calculation. 1922-

The Magic Brain Calculator was a device used many years ago (mabye 1950's) to solve maths problems. It requires you reset it to all zero's to begin with and after a bit of practise you can solve many types of mathematical calculations. Clearing the device is just a matter of pulling the metal bar at the top of the machine and pushing it back in. Calculations of up to 8 digits can be performed such as addition, subtraction and multiplication.