This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
When this device is placed on the knife, the contrivance works on the same principle as a spokeshave. The first setting peels the potato without any appreciable waste, the other setting may be as desired for cutting slices. - Contributed by H. W. Ravens, Seattle, Washington.