Original Odhner Model 127

The main difference between the Model 127 and the Model 107 is that the Model 127 has a Back Transfer mechanism, whereby a number can be transferred from the result register to the input register for re-use. This is useful for chain calculations, and is particularly desirable on pin-set calculators of the Odhner pattern, where setting the numbers on the input register by directly moving the pinwheels by hand can be fiddly. This is not so much of an issue with key setting machines such as the Facit.