It's got a copyright date of 1940 inside the front cover (and 1938 on the backpage, weird), the first couple of pages extoll the virtues and many uses of this handy Handee tool.
And on the top of page 9, it is found as a useful tool in servicing office equipment; in this case taking a Handee to a typewriter.
Taking a Handee (or a 'Dremel') to a typewriter was not my first thought when it comes to typewriter repair, but it will have its uses. A polishing disk should really make those typebars shine, hoping it isn't a grinding wheel he's using on the keys. The potential for disaster might be greater than the benefits from using such a type of powertool.
The rest (most) of the booklet is an extensive catalog listing of all the types of Handee tool and attachments that are available from the Chicago Wheel and Mfg. Co. of West Monroe Street including project books and a book of plans...