At first glance, this may look like a razor for shaving off one's beard or hair, but it is actually a pencil sharpener. It was used by students in the '70s to sharpen the points of their pencils.
However, with the spread of so-called pencil-sharpening machines, this tool gradually went out of use. Adults at that time would complain, "Children nowadays are so clumsy that they can't even use a knife to sharpen their pencils." Now, there are no adults complaining anymore. After all, it is they who were the elementary school children of those days - all grown up.